Tubb is trying to ride a Sea Pony. After Tubb is thrown off, a pair of Gill Men captures the Sea Pony. Moby and the boys try to free him but Moby is trapped in a cave by a powerful force field and Tom is captured himself. The Sea Pony is taken into a ship while Tom is able to escape at the last second. Moby and the boys must now work hard to save the Sea Pony. The Gill Men try more of their powerful rays to stop Moby to no avail. Moby stops the ship and releases all of the sea animals that the Gill Men had rounded up in their Sea Ark.