Once upon a time, abbess Maria and sisters Arsinoe, Ourania, Agathoniki and Chrysovalanto lived calmly and peacefully in the monastery of Agia Theodouli. Until they discover a man's corpse in the sacristy and their lives turn into hell... The investigation of the case is undertaken by the experienced police officer, Miltiadis Sofianos, and his rookie assistant, Hector Tsakalakis, with orders to conduct the investigation in strict secrecy. Sofianos and Tsakalakis have the nuns as prime suspects and interrogate them. Strangely enough, none knew the victim and none saw anything suspicious on the night of the murder. However, evidence soon comes to light that indicates the opposite: one of the nuns secretly put the victim in the convent and then murdered him.