Gilligan is scared at night when the Skipper tells him to watch the signal fire. However, the real fright comes the next morning when Gilligan awakens to a creepy man leering at him on the beach.
Gilligan tells the Skipper that Dr. Boris Balinkoff will be rescuing them. Skipper doesn't believe him until he sees the doctor for himself.
After everyone is introduced, the men discuss the rescue. Dr. Balinkoff only has a small boat, but Gilligan suggests that he and the Skipper can leave and then sail the doctor's yacht back. As Dr. Balinkoff takes Skipper and Gilligan, he remarks, "At last, I have found two perfect specimens." Realizing his blunder, he conveniently picks up two shells from the ground.
In a scary castle on a scary island, Dr. Balinkoff acts friendly. He tells them that he forgot that his crew took the yacht for repairs. After they meet the doctor's hulking assistant, Igor, Dr. Balinkoff goes to pick up the other castaways. Skipper and Gilligan are already ill at ease, but it gets worse when they encounter a dog that meows.
Skipper goes searching the castle, and Gilligan finds a cat that barks. He accidentally goes through a secret door, and Skipper soon follows. They find themselves in a dungeon full of torture devices and a skeleton that chatters its teeth.
Later, Dr. Balinkoff reveals that he can transfer the mind of one animal into the body of another one. Now he can do it to people.
All the castaways are locked in the dungeon. Gilligan and Mr. Howell come down, but speak with each other's voice. Mrs. Howell and Skipper are later forced into glass booths, and soon everyone is in another body. Ginger, in Igor's body, is able to break the chains that bind them.
The castaways switch back into their own bodies. They force Igor (in Ginger's body) into a booth, restore Ginger to her original form, and shove the doctor into the booth with Igor. The cat and the dog go into the other, and Gilligan pulls the switch. As the castaways leave, they see Dr. Balinkoff and Igor in the bodies of a cat and dog, and the animals in human bodies.
The castaways return to the island to get a few supplies before boating to civilization, but the boat sinks in the lagoon.