in 2000, linda watson disappeared from her tucson home. ken coffee cup in her wake. three years later, linda's own mother, marilyn. who'd fought for answers for justice for her missing daughter. gunned down with her friend renee in the driveway of that very same home. detectives couldn't dismiss the strange coincidence of two tragedies happening at the same place. to the same family. >> how often are a mother and daughter killed at the same house three years apart? that doesn't happen. >> reporter: when linda went missing, two men were blips on the investigators' radar. first was her ex-boyfriend, j.r. with whom she'd had a tumultuous relationship. j.r. insisted he was at his house the night of marilyn and renee's murders. and his alibi checked out. plus, said detective kelly anderson -- >> there's nothing evidentiary at the scene that would indicate j.r. had any involvement. and he doesn't even match the physical description of the person the eyewitness saw at the scene running away. >> reporter: but then there was linda's ex-husband, davi

but while he was, linda doing child custody exchanges of jordynn he had met david and rosemary watsonint. >> reporter: rosemary, dave's new wife of two months. >> keep your eye on that name. >> keep your eye on that name, yes. >> what is j.r.'s alibi for the night that linda goes missing? >> on the night that linda went missing, j.r. was with his girlfriend. >> reporter: his new girlfriend. jr was already moving on, he said, but he still seemed concerned about linda. >> jr was very helpful, offering di >> but i think cynically sometimes, detective, guys inveigle themselves into an investigation when, in fact, they're part of the -- the scheme. >> sure. that-- that could certainly happen. >> reporter: detectives also had more concrete reasons to suspect j.r. >> there was a domestic incident that they were involved in shortly prior to this. >> reporter: just two days before linda disappeared. she had called the pima county sheriff's department. >> she made a report that j.r. had come to her house on curtis and was banging on the windows and banging on the doors. >> reporter: j.r. said h