The team realizes the sanatorium has only nurses and patients… no doctors. They search the 6th floor and find portraits of the staff, but one portrait is missing. They determine the missing portrait is the Director, who, as a doctor, had a relationship with the nurse and got her pregnant. After being promoted to Director, he leaves her, and she commits suicide. The ghost nurse is now seeking revenge and looking for the Director. (Source: frankly at MyDramaList)