Al and Owen travel back to the Dragon Blood Islands, now carrying the long-lost Dragon Blood Sabre and Scabbard of Invincibility. When they show them to Grandfather, he notices that the four black diamonds that once decorated the scabbard are gone. He tells the boys that whoever took these diamonds must still be alive as the gems are cursed and make their owner deathless. Meanwhile, Captain Gunner receives a message in a bottle asking for help. Princess Haree of Ruby Island and some of her people are being held captive by an evil pirate king named Razor Toe. Al, Owen and Gunner decide to investigate.