They came from deep beneath the earth's surface: grotesque, reptilian creatures covered with slime, forced from their subterranean lair by underground nuclear testing. Setting up an almost impenetrable dome of fog over L.A. to lower the city's temperature and make the surface more habitable, they've emerged from the sewers and cesspools, impervious to attack and mad as hell. Now, Los Angeles has been evacuated, its empty streets shrouded in a permanent twilight. Except for a small band of survivors, the Slime People have the city all to themselves. Holed up in a television station, pilot Tom Gregory, Professor Gelman, his daughters Lisa and Bonnie, and marine Cal Johnson have been left behind doomed to a fate worse than death... unless they can find a way to penetrate the wall of fog that imprisons them.