Five months ago, the apocalyptic 'Jolt' turned the majority of humankind into the atavistic savages Jay Garvey calls 'Hyenas' on account of their insane, shrieking laughter.A terrified Jay is tempted from his bolt-hole in a Liverpool book shop when he learns the whereabouts of the only boat that hasn't been scuttled by the deranged militia leader known as Sergeant Pepper.As a brutal winter closes in, Jay, and the small band of survivors he collects along the way, must avoid death and capture to take advantage of this single, slim window of escape.