An outbreak of apparent kleptomania at a student hostel is not normally the sort of crime that arouses Hercule Poirot’s interest. But when he sees the bizarre list of stolen and vandalized items — including a stethoscope, some lightbulbs, some old flannel trousers, a box of chocolates, a slashed rucksack, some boracic powder and a diamond ring later found in a bowl of a soup — he’s intrigued.