The boys leave the salvage ship when they receive notice that their father has gone missing. They return to shore and locate their father and the missing Pharaoh’s head and put a stop to a plan by Mr. Zufar to sell the real head while also collecting the insurance for the head which was supposedly sunk. In the end, while the bad guys nearly capture them, the rival divers come to their rescue, having earlier revealed that they were searching for a U-boat sunk by Captain Early during World War II. As a result of an earlier rescue the boys performed, the divers were going to give them a share of the treasure and had come to do so when they found them in trouble. While the mystery is solved, the boys discover that the money the other divers were after is actually counterfeit.