Taking a much-needed break from their rigorous schedules, Brains and Tin Tin set off on a working vacation in the Middle East, where they'll be assisting a renowned professor with the recovery of hidden treasure from the bottom of a lake. As our two intrepid heroes embark on their journey, Tin Tin's father, Kyrano, expresses his uneasiness to Jeff Tracy concerning the expedition. ""A beautiful lake miles and miles from anywhere,"" Jeff says. ""What could be safer?"" Kyrano's fears are justified, however, as his evil half-brother, the Hood, has once again compelled him to reveal details about International Rescue's activities. Making a valuable discovery during their very first dive, Brains and Tin Tin anxiously await the next day's explorations. Unfortunately, they may not last that long, as the Hood infiltrates their camp and hypnotizes them. When morning comes, Tin Tin is slumped over in a chair and the professor is clearly injured and sprawled out on the floor of their trashed caravan.