How long does it take a killer to stop worrying about whether he'll ever be caught? A couple of weeks? A couple of months? 25 years? If he's still a free man then he's probably pretty sure he did, indeed, get away with murder. Detectives retire. Witnesses forget. The trail grows cold, never to warm up again. Until, one day, it does.

Keith Morrison with the story of a "Deadly Triangle," tonight at 10pm/9c on Dateline NBC.