james farren: if that gun killed robin, only two people could have done it. katie phipps: i want robin back. i want to be happy. i want what will never be. josh mankiewicz (voiceover): it began with a letter mailed from a sun-scorched stack of cement blocks and steel wire on the dusty plains outside amarillo, texas, randall county jail. we often hear from inmates, but this letter seemed a little different. within the neat lines, the author dangled a promise, i will "give you one hell of a story." now, that was the truth. the tempestuous tale that unfolded was about two family-oriented women, robin and katie, friends from church who fell hard for the same guy, and then, somehow turned on one another with a vengeance. once she suspected something, katie's claws came out. josh mankiewicz (voiceover): the dizzying spiral of betrayal and bad blood between the women exploded into violence ending in a merciless nighttime murder, and years of lies and suspicions. don't be alone with her. she's the kind of crazy that'll kill you. josh mankiewicz (voiceover): keep this

james farren: can't read the plate. can't see inside the vehicle. his vehicle, but we can't prove that. what about katie? we never saw any vehicle come through that security view that looked anything like the car katie was driving that night. josh mankiewicz (voiceover): tantalizing, but not definitive, which seemed to be true of a lot of the evidence against jd. it had taken just four days to file murder charges against katie. but farren, burned once, was reluctant to charge jd without more proof. and so nine months went by. and then the da got a call from robin's mother, jackie, that forced him to act. jd had apparently asked his mother-in-law for a big favor. had me buy him a ticket to go to new york for the weekend. that trip to new york felt phony to you. oh, yeah. josh mankiewicz (voiceover): and it did to farren as well. it's not that far from there to the canadian border. and after talking about it and thinking about it, i said, let's go ahead and make the arrest. josh mankiewicz: your daughter had been married to this guy. yes. and now he's