At the Church of Lost Souls on the island of Mortavia in the year 1480, Father Guru is a schizophrenic and insane priest whom is the chaplain of a Central Europe prison colony. When an attractive prisoner, named Nadja, arrives tried and convicted of infantcide, the lead jailer Carl, recognizes her as his lost love whom abandoned him years ago, and he still has emotional feelings for her. Carl asks Father Guru to spare her from execution, but Guru refuses. But upon seeing the young man's feelings for the young lady, Guru agrees to help Carl in exchange for Carl to rob graves for him so he can sell the bodies to the local medical schools since funds for the church are in short supply. Guru directs Carl to his lead nun and former mistress Olga, whom is a vampire, to conjure up a potion so when Nadja drinks it, it will appear that her heart has stopped and she can be legally declared dead and buy time so she can run off with Carl.
Upon meeting with Olga to purchase the formula for the potion, Olga's only request from Carl is to deliver some of the executed victims to her so she can drink the blood from them. Carl refuses, but when Olga refuses to sell him the potion, agrees to the other deal. During a benediction ceremony in the church, Father Guru gives Nadja a cup of wine as the last rites and upon drinking it, Nadja falls sick and apparently dies. Guru then has Carl intercept her body before burial in the church grounds and Guru revives her with an antedote. Guru lets Nadja stay in the church tower so he can send Carl away on grave robbing business while he assigns his simple-minded hunchback assistant and bell ringer, Igor, to look after Nadja. Naja begins to strike up a friendship with the mentaly retarded hunchback whom also takes a liking to the young lady.
Meanwhile, Guru is shown to be not only engaged in conversations with his alter ego in front a mirrors, but also a bloodthirsty killer. Guru kills a young sailor whom shows up at the church asking for a private sermon. Guru then delivers the body to a medical school for cash. Then, Guru is confronted by a young runaway, named Christine, in which he lets Olga hipnotize and kill the girl so Olga can drink her blood.
Nadja becomes suspicious to what is happening in the church when she sees people entering the church and not leaving. Then Carl returns from his errands, she wants to leave with him, but he tells her that his jobs for Guru are not finished, but they will leave soon.
The following day, when Father Guru's superior, Bishop Kopel, arrives with his replacement, Father Polanski, since the Catholic Church has deemed Guru not being cabale or running the prison colony, Guru murders and beheads the bishop, and has Igor kill the replacement. When Igor turns against Guru for ordering him to kill a person, Guru and Olga overpower the hunchback and nail him to a wall in a crude cruxifiction shrine. When Guru and Olga begin to argue about what to do next, Guru kills her with a stake through the heart and then attacks Carl to kill him as well as Nadja since he feels that they can serve him no more. But Igor breaks free from his shrine and attacks the deranged priest only to get stabbed to death, but Carl takes advantage of his to throw Guru off a balcony in which the twisted priest gets his neck literally tied in the church's bell rope, and he is strangled to death. Carl and Nadja then flee from the church, free to start their new lives for themselves.