At the center of the crime story is the very large Kremp family, living in the family villa with other relatives and a subtenant. The parents had four adult children, two sons and two daughters, one of whom recently died. The investigation focuses on the recent death of their son Jan. The young man was considered the family "fool", whom no one except his mother liked, because he played various mischievous tricks on everyone. However, his death, as Captain Exner investigates, was not an unfortunate accident, but a murder. Who could have been interested in his death? Was the murderer someone from the immediate family? Captain Exner is looking for a motive...