An outbreak of kleptomania at a student hostel is not normally the sort of crime that arouses Hercule Poirot's interest. However, the warden of the hostel is his secretary Miss Lemon's sister, and efficient Miss Lemon is less than efficient when worried. To set her mind at ease--and decrease the number of mistakes in her typing--he agrees to meet with Mrs. Hubbard. When he sees the bizarre list of stolen and vandalized items--including a stethoscope, a box of chocolates, a slashed rucksack, and a diamond ring (which was stolen, then discovered in a bowl of soup)--he congratulates Mrs. Hubbard on a 'unique and beautiful problem'. But Poirot soon has more than a possible petty thief on his hands when murder enters the picture.