here's josh mankiewicz with "lauren's promise". ♪ ♪ ♪ >> graduation at the university of utah inn saltcity, home of the utes. a time for selfies, smiles and celebration. in may 2019, 8500 graduates and their families packed the universities huge arena. lauren mccluskey should have been here to, receiving her degree in cap and gown. as happy as her classmates. except she wasn't. and the story of what happened and why is as sad as it is eye-opening. >> this wasn't one of those things where it was out of everyone's control. it wasn't like a natural disaster. >> how many times two women have to call for help before the university of utah realizes, you know what, we ought to step this up? >> what are the two of you thinking at that point? >> i couldn't really fathom what had happened. >> neither of us slept at all that night. >> it's a story that could so easily have ended differently. if just one person had stepped up. if just one more phone call had been made. one dot connected. instead, the repercussions of a preventable murder would continue for years to come. >> lauren grew up in the c

here is josh mankiewicz with "secrets from the grave". >> wander through any graveyard, and you willthem, mysteries etched in stone. lives cut tragically short by war, disease, misfortune, and sometimes murder. many who rest in these peaceful places took secrets to their graves. but some here are mainly awaiting. waiting for someone to take interest and ask questions. as you are about to see, the dead can be exceedingly patient. our story begins on a frigid march night in 2009, with a house fire in stow, ohio. that fire was important. not for what it destroyed, but for what it illuminated. >> 9-1-1, where's your emergency? >> it's uniondale drive. there is a fire. >> the house, or what? >> the house. >> the caller was a 16-year-old girl who told the 9-1-1 operator that she, her parents, and her younger brother had all escaped, but barely. and then her father took the phone. >> i don't really understand. it -- the entire front of our house is just engulfed. >> okay. i'm glad everybody got out. >> that dad was scott purk. you will be hearing a lot about him. purk said his family had be

here's josh mankiewicz with "a promise to helene". >> 40 years is a long time. that's 40 winters here in colorado. and countless snowfalls. it was on a day like this that young woman disappeared. her name was helene and helene had a friend named kimberly. a friend who kept her word. you have any idea how many years you were signing up for when you made that promise? >> no. >> for those nearly four decades, kimberly kept her promise. 40 years looking at faces. 40 years meeting with detectives. 40 years retracing helene's steps. >> when i make a promise and make a commitment i follow through. >> helene never knew it but she had another friend. you never met helene. you feel like you know her? >> i do. i feel like i know her well. as well as i possibly could. >> shannon was three years old when helene disappeared. it wasn't until 2019 that she accepted a challenge. >> i had to win. i wanted to win for helene. helene pruszynski grew up as the baby daughter in a close knit family of five in hamilton, massachusetts. >> everybody that met her liked her company. >> jane

josh mankiewicz: and while you're running, they're still shooting. i'm still hearing shots.

here's josh mankiewicz with toxic relations. >> what was wrong with linda curry? >> something is happening with you lynda, you're ingesting something in your body that shouldn't be there. >> she went to the doctor. a lot of doctors. >> and it wouldn't go away. and it will get worse. nausea, vomiting >> dizziness, confusion. >> medicine didn't seem to help her. >> you could have respiratory failure within a number of minutes. >> those who knew lynda watched something unfold. but what exactly did they see? it would take 20 years to unravel this mystery. linda curry, born linda kilgore, with six years younger than her sister pat. linda grew up to be a southern california beauty. she loved the sunshine, horses and family. pat's daughter ricky looked up to her aunt linda. >> she would call me over to her house to go read her closets and i would leave with my backseat loaded from the floor to the roof with clothes. >> she sounds like a lot of fun. >> she was a lot of fun. she was a blast. >> linda worked from the power company, southern california edison, that's where s

josh mankiewicz (voiceover): after more than a year in jail, katie phipps was suddenly back in the arms no longer accused of murdering robbyn spielbauer. not everyone in amarillo was sharing in the love. including robbyn's parents jackie and steve. >> when we got the call it was like what? you are releasing her why? >> what was your reaction? >> disbelief. at first. >> and anger? >> quite a bit. >> i mean, you understand it fits intellectually but there is a father in there who is watching the woman accused of killing his daughter being let out of lock up, she was angry, i'm guessing you are pretty angry. >> i wasn't happy by any means. >> robin's friend erin had a different reaction, not so much rage as resolve. >> at that moment i shifted and i knew we had to get j. d.. i knew that if she was innocent, he was 100 percent guilty. >> da james ferrell admitted publicly that he had made unthinkable mistake. you have the wrong person in jail for 15 months. >>467 days. >>that is not how this is supposed to work. >> no, but, no human system is perfect. the investigators basically followed th