replaced by a mystery. >> she never returned for lunch. >> we did consider that her husband made known that she was having an affair. >> where was? she >> there were no. answers >> nearly 30 years, 60 investigators, and it all kept coming back to one elusive suspect. >> he just very commonly said, i know how to get rid of a body, so it would never ever be found. >> him, some -- >> it was basically an hour never situation. >> hello, welcome to dateline. when kathy had cole disappeared, police didn't know if they are dealing with a missing person case or cold-blooded murder. with little evidence to go on, the investigation grew cold. decades later, a young detective who was just a kid when kathy vanished, dusted off