>> kristine kupka dropped from sight in the fall of 1998. her sister kathyed retired detective gil alba to prove she wasn't simply missing but murdered. >> one of my first steps in conducting the investigation is come where the last place that kristine was seen. >> it was an unusually warm day in late october. accompanied by her boyfriend, rudy persaud, kristine kupka left her brooklyn home with just a light sweater and her handbag. kristine's sister kathy was home sick with pneumonia. >> she called me around 12:30 and rudy was there. she said, kathy, i'm going with rudy to see his new apartment in queens, and i hope you feel better. i'll call you later this afternoon. >> that was the last time kathy was to hear her sister's voice. >> she went willingly, but before that there was a history of rudy and kristine, and she did fear for her safety at some point. >> and i called and her roommate said kristine never came back. i said oh, my god, he killed her. >> those who knew kristine say she would never run off as police had suggested. friends say 28-year-old kr