The mutinous crew tries to send Polly, Captain Coward and Shoeshine Boy to Davey Jones' Locker. But Shoeshine Boy hides behind a rock and becomes Underdog! He bests the crew and saves the Captain and Polly. With Underdog helping to supervise things, the expedition heads for the South Seas Isle to find Fearo. It turns out that the Isle is even more dangerous than the ocean. As our valiant troupe encounters a group of meat eating dinosaurs, only Underdog is able to defeat the creatures... but at the cost of sapping his super powers. And so, as our hero becomes weary, Fearo comes out of the brush and comes menacingly towards the expedition...