In 2000, construction manager Darrell North was found dead in his work trailer in Ft. Worth, Texas. When investigators arrived, they found that he had been stabbed 46 times, described as overkill and indicating a personal relationship between the victim and the attacker. Police hoped that, during the struggle, the killer had left some of his own blood and his DNA behind. Their challenge was to find it. Forensic science points to an unlikely suspect.