Ted Bundy, John Wayne Gacy, Jeffrey Dahmer, Richard Ramirez. These are some of America's most monstrous serial killers. They are the killers who were caught.

Sometimes, despite law enforcement's best efforts, heinous killers do escape justice. Townspeople notice an unusual pattern of inexplicable disappearances. Police become alert to a mass grave that should not be where it is. Investigators unearth a succession of bodies, all having been killed in the same way.

But when there is no face to attach to the perpetrator of these acts, where there is no name for the phantom walking amongst them - how much more unnerving the horror! People begin to mistrust their neighbours' motives and intentions. They fortify their homes and become wary of going out at night. And their suspicions grow and grow ...

These are America's unidentified serial killers.