Dr. Fuwa, a disgraced physician, travels to a remote island to investigate a mysterious illness affecting a nun-in-training who falls into a nightly coma. As he explores the island's religious fervor and the suspicious behavior of the church's leadership, he discovers a history of disappearances and a cryptic warning left by a former nun. However, his investigation takes a dark turn when he becomes personally entangled with the church's staff, leading to a shocking discovery about the island's true nature.
After Makoto and Ririka fall victim to mysterious illnesses and nightmares, Doctor Fuwa uncovers a sinister plot involving a cult led by Father Musili, who made a pact with the Devil to sacrifice virgins for power. To defeat the evil priest, the girls must unite to perform the "Tres Marias," a powerful combined prayer capable of destroying the Devil's influence and restoring peace to the island.