A dead man is discovered in the machine room of the Randlingen sanatorium and nursing home. The man is Dr. Ulrich Borstli, the director of the institution. Constable Studer from the cantonal police takes over the investigation and soon realizes: it was no accident! The hospital director must have been beaten to death with a sandbag around midnight. The search for the perpetrator and motive proves difficult. The patient Pieterlein comes under suspicion because he has been on the run since the crime. However, Studer doesn't really believe in this solution and examines the friendly façade of the psychiatrist Borstli. He soon realizes that the solution must lie in the treatment methods of the nurses and doctors...