a towel under the bedroom door, a fan blowing, and a bathroom window open. that was because the toilet in the master -- mark said he wanted to keep the smell out of the rest of the house. kathy's family knew about the problem with the toilet, but they figured, there was a different explanation for the towel, the fan in, the open window. they believed mark knew there was carbon monoxide in the house, because he had somehow put it there. and he was protecting himself from poisoning. >> how did you respond to that? the suspicion that was placed on you. >> i was devastated. >> five months after kathy died, her case file landed on the desk of a veteran detective, clyde bright again. >> what's your instinct? >> in reading the reports, i was sure that the water heater, the furness, and the vent, and fireplace were not the source of the carbon monoxide. so, you have to think, okay, what else in that house could