The Castaways are frightened as the sounds of battle, including hand grenades and machine guns, rock the island. The culprit turns out to be a gorilla who has found an old WWII weapons cache.

Gilligan is bitten by a bat, and then dreams that he has turned into a vampire. Fortunately the Professor knows about bats (what DOESN'T he know about?!), and is able to identify the bat that bit Gilligan as a common red fruit bat, rather than a vampire bat.

Gilligan meets his double, a foreign spy who has undergone plastic surgery in order to look like Gilligan (why, we're not sure!). Gilligan gets in lots of trouble as his double steals Mary Ann's pies, etc . . ..

Someone kidnaps Mrs. Howell, Mary Ann, and Ginger, and then demands ransom money. The kidnaper turns out to be a compulsive gambler who fled civilization to avoid temptation. While the Castaways attempt to rehabilitate him, he ends up leaving the island, accompanied by Mrs. Howell's pearl necklace, Mr. Howell's wallet, and Ginger's earrings!

One by one, all of the Castaways mysteriously disappear. Gilligan then dreams that he is Dr. Jekyll and Mr. Hyde. In the end, Gilligan rescues them from the hidden World War II munitions pit that they have all fallen into.

A drab, plain-jane woman lands on the island seeking privacy. The girls give her a beauty make-over to lift her spirits, and she ends up looking like Ginger's twin. While the castaways were hoping to lift her spirits enough so that she would want to return to civilization (she has a boat, but has hidden the key), she ends up leaving them on the island and going back to Hollywood to attempt to assume Ginger Grant's movie career.

The Professor determines that a manned space craft will pass over the island, and attempts to fashion a telegraph machine. When that fails, the Castaways try to spell out SOS using burning logs as a rescue signal, but Gilligan catches fire and runs into the logs, causing them to spell out SOL, the name of one of the astronauts! Blooper watch: as Gilligan is lighting the logs, you can see his pants smoking before he backs up into the flaming logs!