"Skinwalker" is the Navajo term for a demon in human form. But no mystical beast was as frightening as the true-life fiend who for four years spread fear throughout the deserts of the Shiprock, New Mexico area. The nightmare began on Thanksgiving 1996, when a feast of horror was served up to Joseph Fleming, 24, and Matthew Trecker, 18. Both young men were stabbed and slashed to death in an alleged attempt to cover up a robbery. The reign of terror continued as a woman was subjected to a grotesque sexual assault--but somehow managed to escape with her life. Donald Tsosie, 40, wasn't so lucky. After leaving a local watering hole, he was savagely bludgeoned, stabbed, and left to die. On June 9, 2000, Betty Lee, 36, was stabbed and then slain with a sledgehammer after being stripped of her clothing. Justice finally arrived in the form of county detectives Bob Melton and Tyler Truby, whose investigation zeroed in on hulking, hate-ridden Robert "Bobby" Fry, a misfit with a taste for brutality. Aided by Navajo trackers, Melton and Truby conducted a sleepless two-and-a-half day manhunt to bag the killer before the trail went cold. Then, like the Hero Twins of local legend, they brought a monster's murderous rampage to an end.