His name is Mobius, and he is death. He has left a trail of corpses stretching from Denver to Los Angeles. Now fate has handed him a new kind of weapon, the deadly nerve gas VX, which can multiply the body count by a factor of hundreds. For FBI Special Agent Tess McCallum, it's a race against the clock to find Mobius before he stops the city's beating heart. But Mobius is closer than she knows … and Tess herself may be his next victim. "Unrelentingly suspenseful, this psychological chiller is only for those with a high terror threshold."—Publishers Weekly Michael Prescott is the New York Times and USA Today best-selling author of more than 20 thrillers.