Miss Amelia Butterworth is unmarried but quite content as an observer of human nature - until late one evening she notices a man and woman enter the supposedly empty house next door, whose owners are away on a trip abroad. Suspiciously, the man leaves the house some time later, but the woman doesn’t follow. The next morning Miss Butterworth finds the woman dead, mysteriously crushed under a cabinet. When Detective Ebenezer Gryce takes on the case, Miss Butterworth decides to take matters into her own hands and solve the murder herself.