Washed ashore in the North Atlantic, Ryan Cawdor and Doc Tanner discover two islands still pristinely intact after Skydark, but whose inhabitants suffer a darker, more horrifying punishment. A hideous strain of mutation infests, turning some into half-monstrous giants with an unquenchable thirst for blood.

The Nightwalkers unleash a hellish feast of horror when the sun goes down. Now Ryan and Doc struggle to survive this enclave of unimaginable terror, trapped in a baronial conflict between the rulers of night and day, with only one way out -- internecine war in a world of the damned....