Product tampering. Innocent lives. Nice suburban homes. A Seattle food company is victim to an ingenious extortion that has the FBI two steps behind. Seattle's veteran homicide sergeant, Lou Boldt, and police psychologist Daphne Matthews approach the case from opposite ends: one undearthing micoscopic evidence, the other putting together a chilling psychological profile of a man willing to contaminate and kill if necessary.

The cop Daphne Matthews secretly loves is being destroyed by the extortion. Boldt sees his department cracking. As the high-tech manhunt builds to a furious crescendo, Boldt and Matthews are jolted again: the madman they're hunting may not be working alone . . .