In 17th century Smolensk, a priest is sent to investigate a convent plagued by demonic possession, specifically Mother Joan, who has already been tried and failed by four other priests. As he delves deeper, Father Józef Suryn finds himself entangled in her web of seduction and corruption, ultimately succumbing to his own desires. The film's dark exploration of the supernatural and human frailty won it a Special Jury Prize at the 1961 Cannes Film Festival.