The Widgeons, a party of boy scouts, are robbed of the £50 that was drawn from the bank in order to buy equipment for camping. Fortuitously, a ‘Mr. X’ appears on the scene, learns of the tragedy, and offers to replace the stolen £50 on the understanding that the loan will become a gift if the boys succeed in discovering the identity of their would-be benefactor. With zest, every scout forthwith becomes a sleuth. But the task proves to be a tough one, involving the Widgeons in all sorts of perplexities and dangers.