>> that's all for this edition of "dateline extra." i'm craig melvin. thank you for watching. months and months. there's a lot of ways to kill someone, but i've never seen anything like this. >> a devastating mystery illness. >> she was in a lot of pain. she was in excruciating pain. >> i saw her walking like -- >> like a zombie. >> like a zombie. >> i knew she was gone! >> what was happening to this young mom? >> so when you're seeing this -- >> we're like "oh my gosh!" someone said, "could this be a poison?" >> this is the kinda stuff that was used by russian kgb agents. >> who in their right mind would even think of this?

>> you need to search those computers. you need to search those phones. >> this is being done to her one purpose and she is in danger. >> this evil came into our lives. i said "how can this be?!" >> a murderous plot. a confounding mystery. m could anyone solve it in time? i'm lester holt and this is "dateline." t here's natalie morales with "the prussian blue mystery. >> reporter: from the moment the ambulance arrived at this san diego emergency room in march ri 2018, the situation was er frightening and desperate.tu triage nurse laura comstock took one look at the young woman on the gurney and knew something was terribly, terribly wrong.

>> she was losing her vision. she couldn't feel her extremities, her feet and her hands. she couldn't even see the water that i was giving her.dn >> reporter: the patient's name was brigida uto. she had just turned 28, yet she seemed to be near death. >> at that point, i mean, she was very, very sick. was probably the sickest patient in the e.r. at that time. i told my coworkers she might code on me.wo >> reporter: whatever was killing brigida wasn't evident. there were no bruises, no wounds, no obvious signs of infection. and yet, when dr. jeff lapoint examined her --oi >> she was critically ill. she was very ill. >> reporter: so began an unusual detective story. s

first, the doctors had to unravel a medical mystery.to and soon enough, real detectives would be on the case too. but at that moment -- >> we saw someone who was almost -- almost apathetic. didn't have a personality. and she could barely talk and tell us anything. it was really hard to get a history. >> reporter: looking for clues, dr. lapoint dove into her ep medical records and they were r extensive. brigida had been suffering for months.uf nausea, fatigue, excruciating pain.e, she'd been in and out of doctors' offices and e.r.s repeatedly. o her sister, olga, says brigida's illness would come on suddenly. >> she was, all of a sudden, violently sick. had to call out from work and just sick for days. >> reporter: various doctors had come up with theories from fibroids to cancer. >> there was one doctor that actually told her that, "oh, you just have really bad menstrual cramps." 'cause she felt -- like, one of

her symptoms was she felt that l her ovaries were about to fall out of her body. and she called me. and she told me this. and she was crying. and she was upset. she was like, "i don't know what to do." and i'm frustrated. because no one can tell us what is wrong with her. >> reporter: brigida had wondered if stress could be making her sick. she had a toddler to chase around, a husband in the navy ha who was trying to find a new career, and a new job teaching special ed. it was thrilling, but overwhelming. so doctors put her on medication for depression. but then she got sick again. >> and she kept going to the doctors. and she kept feeling worse and worse and worse. and then she started losing a lot of weight. >> reporter: brigida's mom, also named olga, felt helpless as he> daughter's illness progressed. >> yes. >> seeing your daughter waste away? >> oh, yes. she was getting tired of going to the doctors and -- and them finding nothing. she says, "mom, i give up.

i'm not gonna go to the doctors anymore." i said, "no, you can't. you have to go back. you can't give up." she was not even walking normally anymore. >> reporter: just when it seemed things couldn't get worse, a disturbing new symptom. >> i went next door to see her. and she -- we ended up on her kitchen floor. and she was crying to me. and she said she had pulled out a chunk of her hair like, just in the shower. it came out. >> reporter: brigida's beautiful dark brown locks started falling out by the fistful. >> when you're seeing her lose her hair -- she felt that that was her most beautiful trait. >> yeah. >> how concerned were you? >> we were very concerned. >> i think march 5th is when she called me in the morning and said, "mom, i need to go to the hospital, 'cause i can hardly breathe." >> reporter: brigida lived in

the country, in a house right next to her parents and yet that morning, brigida couldn't really see her way to their place. and the pain in her legs was so bad, she could barely get into her mother's suv. >> so i tried to help her by raising a leg. but even the touch was painful. she screamed. >> reporter: her mom raced her to the naval hospital in san or diego.al >> she said, "mom, just drop me off as close as you can to the entrance." and -- and -- i still remember, i saw her walking and she walked like -- you know, the -- "the walking dead." >> like a zombie. >> like a zombie. it was horrible. >> reporter: but the navy doctors couldn't figure out wha: was wrong either. f brigida's husband took her back to their family doctor, who called an ambulance when he saw how sick she was. now at kaiser hospital, she was

dr. lapoint's mystery patient. >> one of the emergency physicians who was working, he saw her and said, "it's just not right."sa and from there, our team was called. >> reporter: dr. lapoint has board certification in medical toxicology, a rare thing in an m e.r. as it happened his expertise would prove critical.en >> as a medical toxicologist, i'm a little bit more of -- in the detective, like, role. >> reporter: so what was causing brigida's hair to fall out? not to mention the severe pain, vision loss and weakness? >> the doctors, when they first saw her, said, "oh, it could be, you know, lupus or" -- >> right. she had, like, this chronic kind of withering, slow course. and so autoimmune stuff was on the list. malignancy's on the list. although, not -- cancer doesn't make you lose your hair. it's the chemotherapy that makee you lose your hair. >> reporter: dr. lapointe knew he had to solve this mystery fast. brigida was fading. the clock was ticking.

>> when i saw her, and i knew she was dying, she was in a lotta pain. she was in excruciating pain. and i remember being in the hospital room. and she was like, "i wanna be close to my sister." and she, like, put herself through an insane amount of pain just to turn her body, so she could look at me. >> how close was she to dying? >> i watched my sister almost die. i knew she was gone. >> when we come back -- a race to unravel this mystery! >> your daughter's getting weaker. >> weaker and weaker. >> she was losing her vision. >> she was losing everything. >> were her husband and young son in danger, too? >> i have a child in the equation now. i have a spouse. let's make sure the child's safe, make sure that they haven't been exposed.

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>> reporter: here at kaiser permanente hospital in san diego. brigida uto was so weak, she couldn't even conjure up the energy to care about what was happening to her. doctors have a term for patients in this apathetic state: "la belle indifference." >> you've lost your hair and you can't walk and you're wasting away you're so sick you don't have the insight to -- to go,

oh, my gosh, i'm really sick. it's almost just like, oh, it's fine. >> and that tells you right there, like, she was as sick as she could get and possibly was near death. >> i think so. yeah. >> reporter: dr. jeff lapoint didn't know for sure what was making brigida sick. but to his toxicologist's mind, her symptoms indicated she might have been exposed to a toxic chemical. and he realized she might not be the only one. >> there's so many moving pieces. i have a child in the equation now. i have a spouse. and let's make sure that we're observing them, make sure the child's safe, make sure that they haven't been exposed. >> reporter: he had brigida's husband and son admitted to a separate hospital for testing. and, for safety's sake, he banned all visitors from brigida's hospital room. even immediate family. >> and there was a time where you didn't know what was happening with your sister. did you think, "this is it. she might be gone already, and nobody's telling us?"

>> yeah. oh, yeah. i was like a zombie, a walking zombie, just going through the motions and hoping that she's okay, knowing that b -- if they hadn't called me to tell me that she's gone, it's because she's still here. >> reporter: olga is two years younger than brigida; they've always been close. >> we shared a bedroom, when we were little. so of course, we had -- like, every night was like a sleepover. >> we did everything together. we literally were there for each other for everything that happened through our childhood, teenage years, adult life. you know, she was my go-to person. >> reporter: their dad john mcinvale had worked for u.s. customs at the border. they'd grown up in rural san diego county. >> there's no real dangers. it's a safe, idyllic upbringing for your daughters? >> it -- it -- it's safe. i -- every place has its dangers. i mean, we -- over the years we've had, you know, a rattlesnake here or there or -- or -- you know, somebody came through and stole a pickup truck. there's dangers but that goes with anywhere, you know, in you can't protect 'em from

everything. >> reporter: from their dad the girls learned caution. from their mom, they learned the importance of faith. >> i put 'em in a catholic school. they teach you a lot of moral values and things that are important in life. >> and brigida would beg to go to church during the week. is that true? >> during the week. yes. >> reporter: the little girl who begged to go to church grew into an accomplished young woman who ran cross country and excelled in school -- >> did she put a lotta pressure on herself then -- >> oh, yes. --to be perfect? >> always. always. she's always been that way. even in kindergarden they used to get a lot of homework and shes the type of girl that if she made a little mistake she didn't want her pages to show that she had erased something. she would start all over. >> reporter: near the end of her senior year in high school, brigida met a young man named race uto, a runner like she was a grade behind her but ambitious and determined to go to the naval academy in annapolis.

>> when did you first hear about race? >> i was 16 years old. i remember she met him at a car show. she was there doing the event for her graduating class. he didn't go to our high school. but he was there. and then i just remember her saying something afterwards, like, "i met this guy," basically. and i was like, "oh, okay." i didn't think much of it. 'cause my sister didn't really, like, date that much. >> reporter: but as olga got to know him better, she thought race might just be the guy brigida needed. >> she was always very, like, into her books, very, like, she stuck to the rules. he took her to that adventurous part of her life. >> kind of got her out of her shell? >> oh, definitely got her out of her shell, i saw a different side of her when she was with him. >> reporter: race made it to the naval academy like he wanted, but he suffered a hernia that never healed properly and eventually he had to withdraw without graduating. he did join the navy, though. then in 2014, brigida and race married and very soon she was pregnant with their son.

everyone was thrilled when the baby came. >> we were all excited, really. we'd sit there like -- like when we were little. and we had a little doll. we'd hold my nephew. and we'd take turns. and like -- you know, like, i'd take care of him, while she was sleeping or trying to rest. watching her learn and, like, experience being a mom for the first time, how she wanted to be, it was beautiful. >> reporter: then just before her son turned two, brigida got sick. soon she could barely pick up her child. >> and your daughter's getting weaker -- >> weaker and weaker -- >> and she's -- can barely walk. she was losing her vision. >> she was losing everything. >> reporter: now, in the hospital, toxicologist jeff lapoint developed a chilling suspicion about what was wrong with brigida. >> we're all just, like you think? oh, my god. >> reporter: a rare and devastating diagnosis.

>> highly toxic. >> highly toxic. >> this was your very first case. >> yeah. >> reporter: growing danger at the hospital and a sudden alert at the fbi! >> we were notified immediately that's something we're very concerned about. >> reporter: when dateline continues.

reporter: like any good detective, dr. jeff lapoint was keeping his mind open, letting

the clues lead him to a theory about what might be killing brigida. >> i just got to figure out what's wrong and get the treatment started. >> reporter: most of her symptoms could have been caused by a range of toxic chemicals like arsenic, cadmium or cesium. but to dr. lapoint, one particular symptom stood out. sudden hair loss. >> that's the telltale sign. i think that any medical toxicologist, if you tell them that you have a young woman who has lost her hair and now can't walk because her feet hurt so bad -- thallium's going to be on our list. it's like straight out of the books. >> reporter: thallium is a heavy metal, atomic number 81 on the periodic table of elements. >> it was discovered late 1800s, and then quickly began being used medically in the early 1900s as, like, a depilatory agent. if you had lice or something, you wanted a child to lose their hair, they would give them thallium.

right? >> reporter: oh my gosh. dr. lapoint also knew that for decades, thallium had another use, as an ingredient in rat poison. >> and it was really, really good as rodenticide, that was outlawed in the 1970s. it's really good at killing things at the end of the day. >> reporter: highly toxic. >> highly toxic. >> reporter: you had never treated anybody else for thallium poisoning. so this was your very first case right there -- >> it was. >> reporter: -- in front of your eyes. >> yeah. >> reporter: yet there was no quick way to confirm his suspicion. hospitals rarely see patients with thallium poisoning, and don't have a way to test for it. >> so no hospital is just gonna put a drop a blood in and have it come back, yes, thallium. right? so you have to send these things away. so now i'm looking at a two to three, maybe, day delay. >> reporter: days that he knew, brigida might not have. >> we have, like, a really scary situation where i have a test that's infrequently ordered that i need now -- that is a send out. right? it's scary. it's serious. it's infrequently done.

and it's exotic. >> reporter: you're in a race against time when it comes to trying to save her life. >> yeah. so i'm, like, trying to advocate to all these different people -- lots of hours on the phone. just trying to get someone on the phone and be like this woman's going to die. so as soon as we sent the tests, we said, "how do i get the antidote?" >> reporter: he wanted it ready to give her as soon as results came in. what is the antidote? >> so the antidote's called prussian blue. >> reporter: you've probably seen prussian blue -- in paint. yes, paint. it's been used as a pigment since the 1700s. you can see it here, in vincent van gogh's "starry night over the rhone." but it wasn't until 1965 that scientists discovered prussian blue could be used as an antidote. it works by speeding up elimination of certain poisons, such as thallium. but while you can buy blue paint in any art shop, pharmaceutical grade prussian blue is nearly impossible to find. >> and so we started calling pharmacies around town, at different places. we started calling the navy. or, you know, we called our

local public health people. we got in touch with the cdc. and we finally found a storage, you know, kind of -- they're all, like, confidential storage sites. but we found one up in los angeles. >> reporter: prussian blue is so hard to get because it's also an antidote for radiation poisoning. the u.s. government keeps it under close guard, stockpiled in case of nuclear attack. >> so no one really wants to give me an antidote before i've proven it, right, 'cause we don't just throw around prussian blue, like, we keep them in stores in case there's a dirty bomb. >> we have several tripwires set up. and in this case the patient was here in san diego. we were notified immediately of the prussian order. >> reporter: john gill is a special agent with the f.b.i. in san diego. his focus is weapons of mass destruction. a request for the antidote to thallium poisoning put his office on alert. >> in the past several decades, there's been instances where thallium has been used as an assassination weapon against former spies and former

dissidents. >> reporter: so that's what you're thinking when you get this call first is, "uh-oh. what is happening here in san diego." >> right. that's something we're very concerned about in the united states. >> reporter: all this just as president trump was days away from a trip to san diego to talk about the border wall. you triggered all kinds of alarm bells. >> i triggered all kinds of alarm bells. yes. >> reporter: so when you're seeing this -- >> we're like, "oh my gosh!" >> reporter: a deadly substance in brigida system. but how? >> i said, "i think i have a poisoning case, and i'm proceeding like this is an intentional poisoning until proven otherwise." >> reporter: brigida's mom this is time that matters. a window of time to help protect the ones you love.

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>> reporter: brigida's mom couldn't visit her daughter in the hospital. no visitors were allowed, so she waited and she prayed. that's all she could do. 30 miles away, at kaiser hospital, dr. lapoint was

waiting, too. three days had passed since he sent out brigida's samples, brigida in pain the whole time. finally -- the lab results came back. just as he suspected, it was thallium. a lot of it. brigida's husband and young son seemed to be clear of the toxic metal, but she was in serious danger. >> her levels were off the charts? >> yeah. they were really high. >> reporter: more than a thousand times the acceptable level. >> wow. that's unbelievable. >> reporter: a hospital staffer had driven through the night to get hold of prussian blue pills. dr. lapoint started brigida on them immediately. but-- with so much thallium in brigida's system, dr. lapoint worried prussian blue would not be enough to save her. he also put her on dialysis to filter her blood. it was a slow process.

when fbi special agent john gill arrived to question her, brigida was still desperately ill. >> how would you describe her condition at that point in time? >> it was a very serious condition. she struggled with answering simple questions -- sick as she was, he knew he couldn't wait. >> she looked very bad. and it was concerning 'cause -- at that point we didn't know if she was gonna make it. >> reporter: he needed to figure out quickly how she'd been exposed to thallium. brigida did her best to help. >> she brought up several points where she thought she could've been exposed to thallium she had received holistic medical treatments in mexico. >> reporter: or maybe, she said, she could have been exposed at the school where she worked, it was on an old army base. there might be traces of old rat poison there. >> so some of these older school structures -- they were -- used during world war ii and -- that's the time when they used

thallium-based rodenticides investigators followed brigida's leads -- the holistic treatment, nothing there. san diego sheriff's detective brad farr checked out the school. >> i talked to some other teachers that work in the same area she worked. there had been some rumors that the previous year there were some teachers that were -- went out sick a lot, so i had to look into that. it turned out to be not in any way, shape or form involved with this. >> reporter: meanwhile a hazmat team searched the uto house -- but found no thallium. and, they considered another possibility. >> we also had to explore the fact that sometimes in these cases -- a person may try to poison themselves if they're -- struggling with depression or crying out for -- for attention. >> reporter: brigida had been depressed around the time she first started getting sick. but brigida and everyone who knew her told him no way was she suicidal. >> i told the detective, "i know my sister more than anybody. she would never do this to

herself." >> and as a mother of a young child -- >> no! >> i would imagine, much less. >> no. and she always wanted to be a mother. she always wanted to have a family. she wouldn't throw it away like that. >> reporter: as they eliminated all the other possibilities the detectives along with dr lapoint came to a sinister conclusion. >> i'm proceeding like this is an intentional poisoning until proven otherwise." >> why would somebody choose thallium? >> someone would choose thallium because it looks like a medical mystery. it presents as someone just having a slow decline and withering away and dying -- that you would as -- associate with a chronic illness. it's -- it's poison to get away with it. >> reporter: the next step to solving this mystery was figuring out how brigida had been poisoned. dr lapoint did his own kind of detective work. >> and you see this, i mean, you can see these kind of really bright spots everywhere, like, all throughout -- >> those little -- white. >> yeah. >> flecks? >> those little white flecks. >> reporter: the little white

flecks are thallium in brigida's digestive tract. >> so when you're seeing this >> in the context of what we're seeing we're, like, "oh my gosh." yeah. >> if it's in her gut, what does that tell you about how she was getting. >> yeah. i mean, it's -- i mean, food is -- right, >> somebody is feeding it to her. >> yeah. she's eating it. someone is giving to her yeah. >> reporter: it was what dr lapoint had feared, when he took that unusual precaution that left brigida's family in the dark. >> i cleared everyone out of the room because everyone was bringing gifts and food, everything out, everyone out. a lot of people get poisoned, come to the hospital and get worse if they-if someone else is bringing them more poison. so i just want all the variables off the table. >> reporter: so far dr. lapoint had done a lot of things right. but he knew, against thallium, that might not be enough. >> in a lot of these cases, people don't recover. a lot of these cases, people can't feel their legs again. or they never grow their hair back. >> reporter: even if brigida survived, there was no telling if her life would ever be the same.

coming up -- who could be behind this?! >> your circle is narrowing. you're looking at her family. you're looking at her sister. and of course you're looking at her husband. >> absolutely. >> when "dateline" continues. skip to cold relief fast with alka seltzer plus severe powerfast fizz. dissolves quickly. instantly ready to start working. ♪ oh, what a relief it is! so fast! come on! let's hide in the attic. no. in the basement. why can't we just get in the running car? are you crazy? let's hide behind the chainsaws. smart. yeah. ok. if you're in a horror movie, you make poor decisions. it's what you do. this was a good idea. shhhh. i'm being quiet. you're breathing on me! if you want to save fifteen percent or more on car insurance, you switch to geico. it's what you do. let's go to the cemetery!

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>> reporter: dr. jeff lapoint believed someone was determined to commit the perfect murder, by feeding bits of the highly toxic

metal, thallium, to his patient, brigida uto. for tense hours and days, the doctor and his team fought to save brigida's life. she'd consumed more than enough thallium to kill her. and yet -- >> i don't know why i'm here. i don't -- i don't know why i'm still alive. and that's scary. >> reporter: meet brigida, she's still with us. >> did you feel like you were dying? >> i did. i did, but i -- i was af -- too afraid to admit it to myself. >> what kept you alive in that time? >> my son. wanting to see my son. >> reporter: as the antidote took effect, brigida in essence, woke up. she found herself in a hospital bed with only wisps of hair on her head. but she couldn't walk or really see. and doctor's couldn't really tell her what to expect.

>> they pretty much were -- were very open about not knowing what was going to happen. >> reporter: but then one day, her cell phone came into focus. days later, she caught sight of something else. >> i was really excited because i could see the tv. like, what brand the tv was, across the room. >> small victories. >> right. at first, my goal was to be able to walk with my walker to the door of my room. then after that it became, you know, walk to the nurse's station and then come back. and sometimes they would have to wheel me in. >> reporter: while brigida continued to make a slow physical recovery in the hospital, she also had to face the hard truth that someone had plotted against her. >> we asked her, is there anyone that has an agenda against you or anything? and she vehemently stated that,

"no, i -- i don't think there's anyone in my life that would attempt to poison me." >> reporter: but agent gill knew that intentional poisoning was usually personal. >> statistically and historically speaking, when you do have a poisoning it's either a close family member or close friend. >> reporter: sitting alone in her hospital room, brigida found herself terrified at the thought of doctors lifting their ban on visitors. >> did you start to become more fearful as you started to then realize that this was intentional poisoning? >> yeah. i started getting fearful. i started thinking about what would happen when i got out of the hospital if i -- if i got out of the hospital. and who would i have to protect myself from? >> and i imagine at this point your circle is narrowing as to who could've done this. you're looking at her family. you're looking at her sister.

and of course you're looking at her husband. >> absolutely. >> reporter: they talked to everyone, including brigida's husband race uto. >> he was a very friendly, very cooperative individual throughout the entire investigation. >> was he at all concerned about his wife? >> when we first talked to him in the hospital, he did have some tears. and he kept saying, "i just wish i could do something to help her." >> reporter: he said the right things to the detectives. but special agent gill learned quickly that something about race uto seemed off. >> some of the medical staff had expressed some concern over mr. uto's behavior at the time. it came out that he wasn't acting as a concerned husband should be acting. he was asking the wrong kind of questions. he didn't seem concerned about what was happening to her. >> reporter: suspicious as detectives were, brigida couldn't go there. >> at this point are you

suspecting your husband at all? >> no. >> anybody who had suggested that idea, i had started, "why would you think that -- that my husband would do something like that? like, i -- i don't know. he's the one that brought me here. how does that make any sense?" >> reporter: it was true. race was the one who took brigida to the doctor's that day she was transferred to the hospital. to brigida that was an act of an innocent man. she also remembered how race cared for her as she fell ill. >> as you were getting more and more sick, did he show that he was concerned by bringing you food? was that part of his way of taking care of you? >> that was -- that was his way of taking care of me. when i started staying home, he would bring me breakfast sandwiches in -- in bed. he would make sure that i had food. >> and you're thinking, "wow, he's showing a side. he's taking care of me"?

>> yeah, "he's taking care of me. he really loves me. he really cares about what happens at this point." >> reporter: but brigida also told the detectives something else about her husband. it turned out race had a very strange hobby collecting the types of plant seeds that are used to make poisons. >> and when you hear this are alarm bells going off? >> absolutely. this isn't a normal amateur hobby to have. so obviously it was very concerning for us. >> reporter: sixteen days into brigida's stay at the hospital, detectives had enough evidence to get a search warrant for the uto home. race was there to greet them. >> he was wearing these dark sunglasses. no reason for anyone to wear sunglasses, especially inside your residence. >> reporter: he was fidgety, but seemingly candid. >> we asked him, "well, if we image your phone, is there anything in your search history that is gonna be kind of any concern to us?"

and he said, "no, not at all. by the way i'd recently erased all the search history of all my electronic devices." >> reporter: that made the detectives even more suspicious. they took his electronics. they scoured the house. the garage. and then they got to his car. >> and then within the hole for the spare tire we find an odd mix of materials. a canister of acetone, packets of exotic seeds. >> reporter: still barred from visiting, brigida's family was at home. sister olga called the detectives over. earlier that day, her mother had seen race toss out a black trash bag. >> and i was like, "okay, i'll go get it," >> she's a great junior agent. she actually went dumpster-diving. >> what did you find in that black bag? >> some of the more serious things. so we found receipts for some of the exotic seeds that he had ordered. we saw some of the crude

filtering mechanisms that he had. we found solutions in which to purify and refine some of the -- the poisons. >> reporter: agent gill says they found evidence race had tried to grind up castor beans to make the poison, ricin. he says they also found rosary peas like these, a seed that makes another deadly poison and seeds like these from something called the suicide tree of india. and on race's electronic devices that he thought he wiped clean, they found two books, "criminal poisoning" and "the poisoners handbook." >> reporter: as bad as it all looked, there was one thing they didn't find, thallium. not a trace of it. without that, detectives felt there wasn't enough evidence to make an arrest. at the end of the search, race uto remained a free man. but detective farr knew he needed to warn brigida.

>> so i went to the hospital, and we had a very long talk, and i showed her some of the stuff that we found. basically lay it all out for her that, "if you get out, you need to not go back to your husband." >> reporter: coming up. would investigators get the proof they need? >> i think he thought he had it beat >> reporter: and a haunting, terrifying moment. >> he had made a breakfast sandwich for me. and my son climbed up and wanted a piece. >> reporter: by now - the want the cream winning beauty's best?

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>> reporter: by now - the doctors and nurses, and law enforcement all believed they had to protect brigida from her husband, even if brigida still couldn't wrap her mind around it. >> i know that through all the

questioning they were trying to get me to arrive at that conclusion myself. i finally had gotten to the point where i had told investigators, "fine. you know, continue the investigation, but i need proof." >> reporter: so did law enforcement. they kept digging and learned race uto had a secret life. there was a girlfriend who thought his wife was dead. did she have any inkling or suspicion of what he was up to? >> no. no, not at all. he had taken his son with them on so many of their dates that the -- the son was actually calling her mom. mr. uto painted this picture like he was a former navy seal. and he specifically mentioned he wanted to work for the fbi in the poisons department. >> reporter: kinda like what you do. >> that's very ironic, yeah. >> reporter: then they found another girlfriend. >> he specifically told that girlfriend that he wanted his wife to get hit by a bus and for her to die so he can get sole custody. >> reporter: they asked race to take a polygraph.

he agreed. >> his demeanor during the first half was confident. i think he thought he had it beat. >> reporter: prosecutor paul reizen is with the san diego district attorney's office. >> you could kind of see him do this, you know? just take a deep breath. and it almost looked like, "all right, i got this. i'm gettin' through this. we're good." and then took a turn for the worse for him not us.

>> reporter: the polygraph examiner got in race's face. >> confronted him and said, "i don't believe anything you're saying. i think you're lyin' to me and the tests prove it." and that's when he confessed. >> reporter: right then and there, right after the polygraph? >> right after the polygraph. >> reporter: finally, race spilled the whole story of how he plotted to kill his wife by feeding her thallium, making her suffer excruciating pain for months. he was arrested for attempted murder.

brigida's family felt the sting of betrayal. >> he took us all for fools. he saw people that were willing to love him and open their arms. my parents saw him as their son at one point. i saw him as a brother. and he took advantage of us wanting to be open and caring with him. it was upsetting. i couldn't believe it for a while. i said, "how can this be? right under our nose he was doing all this to our daughter." i thank god that there were no -- they're right next door, because i think if they had been living someplace else she woulda died. i'm sure of it. >> reporter: race admitted he tried to kill brigida three

times by putting thallium in her food. so then you start going back in your head. and you're replaying all the times he brought you food and made you food. was there an instance that stands out in your mind? >> he had made a breakfast sandwich, and taken it to -- to the bedroom for me. and my son climbed up and wanted a piece. and immediately his reaction is, "no, don't give him any of it." i think about that all the time. >> reporter: a moment that could have easily gone a different way; it haunts her. race told law enforcement he doled out the poison based on brigida's weight, starting with one gram of thallium in late summer 2017. >> brigida got sick, but she obviously didn't die. she didn't go into the stages of where she ultimately ended up in march. so he upped it the last time.

he upped it up to five grams. and he thought that was gonna do it. >> reporter: it should have been a lethal dose, but race didn't factor in his wife's will to live. all the doctors, the nurses, the detectives say it's your quiet strength that allowed you to pull through. you believe that too? [ laughter ] >> yeah, i struggle with that -- >> reporter: don't be humble-- >> -- a little bit. [ laughter ] >> reporter: don't be humble. >> thank you. i mean, i would hope so. i would hope that i -- i have that to give to my son. but i think, it's all the work that they did together that has helped me be here now. >> reporter: and interesting because the telltale sign of thallium poisoning is your hair falling out. in some ways, losing the thing that made you feel beautiful was the thing that saved your life. >> right. >> reporter: her hair is slowly growing back, but the invisible damage is harder to heal. emotionally, how are you doing? >> it's rough. it's still hard to stop and think about it, about what happened, the amount of deception, the amount of -- just i can't really trust people. and what i've discovered is, you know, trusting myself is -- is difficult too. >> reporter: race uto pleaded guilty to three counts of

attempted murder. he's serving 21 years to life. before they were married, brigida told race that as a catholic, she believed marriage was forever. how do you feel about divorce now? >> yeah. [ laughter ] i love the idea. >> reporter: brigida has filed for divorce, but for now she's still legally married to the man who tried to kill her. ♪ but this strong woman, who couldn't walk not that long ago, is now running again. >> it's been hard when at first i could -- i couldn't even walk without a walker. so -- >> reporter: oh, my gosh. >> so it's been a very slow -- slow progress. >> reporter: is this your therapy now? >> yeah, yeah. i remember being in the hospital and finding out that -- everything out, and being so angry that i couldn't get up to go for a run. [ laughter ] >> reporter: brigida is hopeful, but her troubles are far from over. race left her in debt. she worries about losing her house. she's physically stronger, but even recently, at school she had to hold on to the board to keep her balance.

she worries about how her son will deal with the truth when he's old enough to understand it. right now, though, brigida's focus is on embracing life and >> reporter: you're living life >> that's all for this edition of "dateline." we'll see you again friday at 10:00/9:00 central and i'll see you tomorrow for nbc "nightly i'm craig melvin. >> and i'm natalie morales. >> and this is dateline. >> if you admit that she's never coming home, it's like you're admitting defeat or that she's dead. >> reporter: a hard-working wife. a loving mother. a woman with a complicated love life. >> she was having affairs. >> they worked in the same office areas. they spent some time after hours together. >> kathy was trying to break off the relationship. >> reporter: now the secret was out. replaced by a mystery. >> she never returned from lunch. >> we did consider that her husband may have known that his wife was having an affair. >> where was she?