here's josh mankiewicz with "poison". >> reporter: what was wrong with linda curry?g's happening to you, linda. you're ingesting something that's in your body that shouldn't be there. >> reporter: she went to the doctor. a lot of doctors. >> and it wouldn't go away. and it would get worse. >> nausea, vomiting, dizziness, confusion. >> reporter: medicine didn't seem to help her. >> you could have respiratory failure within a number of minutes. >> reporter: those who knew linda watched something unfold. but what exactly did they see? it would take 20 years to unravel this mystery. linda curry, born linda kilgore, was 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, ricki rycraft, looked up to her aunt linda. >> she would call me over to her house to go raid her closets and i would leave with my backseat loaded from the floor to the roof with clothes. >> reporter: she sounds like a lot of fun. >> she was a lot of fun. she was a blast. >> reporter: linda worked for the pow

here's josh mankiewicz. >> reporter: the american dream. so many of us want it. the loving family. the honest job. the home you can afford. the idea that you can start over here. and in this new country, that better life will be yours. this is a story about that dream. about a family that worked for it. won it. and then what happened to them. >> 911 emergency. >> reporter: this wasn't part of anyone's dream. >> someone just robbed our house. they broke in. they, they tied me and my mom up. >> reporter: how could it happen, in this safe, gated community? in this home they'd worked so hard to have? >> is everybody okay? >> i don't know. they just beat me up. i don't know where my mom is. >> reporter: and who deserved it less than this woman? >> my mom brung the heart to the family. >> reporter: ryan girgis was the baby of the family, spoiled rotten by his mother ariet. >> we couldn't function without my mom. my mom was, like, the chef in the household, counselor. >> the full-service mom? >> oh, yeah, she did it all. yeah, she was really, really nice, sweet lady. >> reporter: she was

here's josh mankiewicz with "deadly betrayal." >> reporter: there comes a time in most cops' careers when they see something so horrific, they'll do just about anything to forget it even though deep down they know they never will. for officer randy mullenex, that moment came in november 2012 on a call to chagrin drive in willoughby hills, ohio. >> you ever have a scene like this before? >> never. i've never seen a crime scene like that and i hope i'd never have to again. it was bad. >> reporter: finding out what happened that night on chagrin drive, and why, would ultimately lead investigators on a journey that would reveal accusations of a diabolical murder plot -- and a series of betrayals that tore apart an american family. that journey would begin when this house of horrors was still the loving home of lisa and kevin knoefel, a couple whose friends describe as destined to be together from the moment they met. >> i remember her talking about him, and she had nothing but great things to say. >> reporter: lisa's close friends, kayleen and karl lessmann, were the unofficial chaperone

here again, josh mankiewicz. >> and that's from -- >> reporter: as prosecutor ebrahim baytieh and investigator of linda curry's death, they found something remarkable, two interviews with linda curry. turns out, after strange things happened with linda's i.v.s while she was in the hospital, detectives had interviewed her, and those conversations were recorded. >> how have you been feeling, since you left the hospital? >> oh, you know, i either feel great -- >> reporter: now, investigator shull put her headphones on and listened to linda curry's voice. >> i'm hard on a lot of things. i'm hard on my men. i'm hard on my cars. i'm hard on my shoes. i was not easy on my i.v. bag. >> reporter: she seemed to be joking about the apparent damage to the i.v., but detectives weren't laughing. they knew linda's friends and family suspected paul. >> i'm going on the assumption right now that paul is doing this, if something is being done. >> uh-huh. >> we can't even prove something's being done. >> uh-huh. >> reporter: linda did acknowledge the suspicions of others. >> all my friends -- a lot of my friends