Four friends are attacked by a demon while on a picnic, due to possession of a tome of mystic information, and find themselves pitched into a world of evil that overlaps our own.

Deep within the woods and canyons of California, four teenagers happen upon an ancient book containing the secrets of a strange, malevolent world that coexists with that of mankind.

Based on the Hammett novel, this ultra-rare film—is nominally taken from the author's classic gang-war novel Red Harvest, which proved too brutal and cynical even for pre-Code Hollywood.