>> reporter: at first it was just a rumor that spread around little crozet, virginia that february, 2003. but pretty soon everybody knew it was true. it wasn't any ordinary fire robert davis witnessed out on cling lane. >> you'd hear about it in the grocery store or -- or the -- the gas stations or stuff like that. >> so it was clear that it was a murder. >> yes, sir. >> reporter: ann charles and her 3-year-old thomas were dead, horribly. the forensics man, larry claytor, got a better look at it than anybody. >> this is probably one of the more horrendous cases i had -- had worked in my career. >> reporter: larry couldn't give investigators much to go on, a few small footprints in the snow out back. but forget dna, any possibility of finding that was flushed away by fire hoses. >> and then i get word from the medical examiner's office that they had recovered a knife that was sticking in the woman's back. and -- >> what'd you think when you heard that? >> i went back to my photographs. and sure enough, in the middle of her back, was the knife. >> reporter: so, someone stabbed her, but who