assassination. it was a hit, no question. >> blind justice. >> thanks for joining us. i'm ann curry. for criminal investigators, it is often the hardest thing of all to find, the motive. in the story you're about to see, the crime took place in florida, but detectives didn't discover an apparent motive until they dug around a tropical island thousands of miles away, something long buried that had nothing to do with treasure. here's keith morrison. >> it was august, hot in coral gables. the air was shirt-sticking thick as night fell. a small damp breeze pushed weakly at limp palm fronds. in the artificial cool of attorney john sutton's house, an intimate party was winding down early. it was susan sutton's birthday. attending, their son, his girlfriend and john's law partner. daughter melissa just off to college in north florida, couldn't be there. so she phoned her mother to say she missed her. you two close? >> extremely. it's my best friend. >> i was going to ask how old your mom was. >> 57. no, you can't put that on. she was a nice 45. let's leave it at that. >> the guests left. th