even though teresa mayfield's husband scott had been very cooperative with investigators, they wonderedmething >>> welcome back to dateline. even though teresa mayfield's husband, scott, had been very cooperative with investigators, they wondered if there was something he was not telling them. here again, with secrets and a small town, is keith morrison. >> it's a funny thing about secrets. they can only stay hidden for so long. especially in a little place lake moundville. and it did not take very long for sheriff ellison corporal boyd to stumble on a secret sky had been keeping. >> while we was out at the crime scene, scott had had a young lady come pick up the boys. it was only later when the fog of grief had lifted, that one of teresa's relatives wonder to police, who was that woman, hanging around the day trees that died? ellis and boyd tracked her down. and what they discovered, well that changed everything. or seems to. the person they were talking to was scott's mistress. >> she was under the impression that scott was not married at that time. >> what did you make of that when y