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. This film was re-editted with additional footage and released as Equinox (1970).

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.

Due to their possession of an ancient mystic book, four friends are attacked by a demon while on a picnic and find themselves pitched into a world of evil that overlaps their own. The film was originally made in 1967 by Dennis Muren as The Equinox: Journey into the Supernatural. Jack Woods was hired to shoot additional footage and expand on Muren's work.