The Blue Diamond

Despite the extreme precautions, the famous diamond is stolen from the Governor-General's suite in the middle of the night, with no clues left behind. With Scotland Yard baffled, Joanna and the Watsons are called in to investigate the theft and it becomes clear that the crime is not simply the work of a master thief, but one that could greatly aid the Germans and turn the tide of war in their favor. Time is of the essence and the blue diamond must be recovered before it causes irreparable damage to the allied war plans.