Homicide detective Ellen Ridley of the SFPD is tracking a serial killer terrorizing young women in the San Francisco Bay Area. Ridley is sure she's cornered her most likely suspect: Stephen Tregear, a hacker and code breaker who works for U.S. Naval Intelligence. But Tregear is not the killer... he's the killer's son. Ridley and Tregear team up to look for Tregear's father, Walter, in an elaborate game of murderous cat and mouse. As the body count rises, Ridley must race against the clock to stop Walter before he kills any more women-and Tregear must finally confront the father who has been trying to kill him for twenty years.