During the World War II, the prisoners of a German camp in a greek island are trying to escape. They don't want only their freedom, but they also seek for an ineffable treasure hidden in a monastery at the top of the island's mountain.

An excommunicated priest sets up a satanic cult that only looks Catholic on the outside. He convinces a man to sign over his daughter's soul so that she will become the devil's representative on earth on her eighteenth birthday, but as that day nears, the man seeks the help of an American occult novelist to save his daughter, both physically and spiritually.