The last member of a mysterious secret society dies. He was a priest and the guardian of a sinister abandoned church in Los Angeles. Another priest, Father Loomis (Donald Pleasence) discovers a strange cylinder and a book in the basement of the church. Inside the canister a gruesome greenish liquid seems in perennial autonomous movement. To clarify the meaning of the manuscript and the baleful nature of the swirling fluid, Father Loomis invites professor Howard Birack (Victor Wong) and his crew of graduated students to study his findings. While the fluid infects some of the students transforming them in a sort of living dead, they learn from the manuscript that the cylinder contains the remnants of Satan and that Satan himself is just the key to a meaner kind of Evil coming from another realm.
