. >> my name is tom martens and we need help. >> reporter: in the early hours of august 2nd, 2015, tomtraight-laced 30 year veteran of the fbi makes a shocking call to 911. his 39-year-old son-in-law, jason corbett, is dead on the bedroom floor. bludgeoned with a baseball bat by tom. it's a gruesome end to a day that began so differently. >> it was saturday. the kids both had play dates. >> reporter: molly's parents were never supposed to be with their daughter that day. but when their own plans fall through, that make a fateful decision to drive over and visit for the night. were they welcome in your home? >> i knew they didn't feel comfortable in my home, but they knew it was beneficial. >> reporter: the martens arrive around 8:30 that evening, bearing a gift for grandson jack. >> i had brought over a baseball bat for jack. he thought it was really cool to get any former baseball gear that was a hand me down. >> reporter: after some pizza for dinner, everyone settles in for the night, with tom and his wife in a guest room in the basement. molly and jason in their room on the first fl