Gruber puts up his various "For Sale" oyster-fishing signs so their customers see them first thing when they arrive. The crew is putting phony pearls into oyster shells, and Gruber figures that someone bites into a fake pearl, the pearl rush will be on. McHale comes over and Gruber quickly has the crew dump the oyster shells into the lagoon. A local native chieftain, Ululu, has been playing gin with McHale and losing big. Urulu sees the baskets of shells and they go over to ask Gruber what's going on. The chieftain says that they won't find any pearls, explaining that a hundred years ago Karatonga--the Serpent of the Lagoon--took all of the pearls.
Later at the base, Binghamton complains that his wife sends him letter saying how his civilian friends are cleaning up. He sees Gruber and Christy setting up a stand to sell oysters. Binghamton has had enough and figures he has enough evidence to get them jailed for profiteering on a military installation. McHale and Parker come over and McHale reminds Binghamton that Rogers sent orders that his crew should test the new torpedoes. Since McHale can't make a test without a full crew, he suggests that Binghamton call Rogers and say that he can't carry out his orders. Binghamton gives in but tells them to leave the oysters. He then tells Carpenter to take oysters to the officer's club so he can eat like a millionaire even if he can't be one.
Later, Binghamton and Carpenter eat and Binghamton bites into a fake pearl. He quickly finds two more in their oysters and tells Carpenter that they have to keep their discovery to themselves. They go to the island's lagoon and harvest oysters while the 73 is out. The 73 returns and Christy blurts out about the phony pearls. Gruber admits that they spiked the pearls and McHale figures that they'll have to tell Binghamton the truth to get out of trouble.
When the 73 docks, Binghamton denies knowing anything about pearls. He says that he's taking over the island to take it over as an officer' recreation area. McHale explains that the crew salted the oysters, but Binghamton tosses him out and says that he has to set up in the swamps.
Later, the crew makes a new camp in the swamps and McHale finally has enough. He and Parker go to Binghamton, who has set up an office on the dock. Urulu and his tribesmen arrive for a gin rummy rematch with McHale. He sees the oyster shells and wonders why everyone is on a seafood kick. When Carpenter brings another pearl over, Urulu says that Binghamton must be nuts. As McHale and Parker arrive, they overhear Binghamton ordering Urulu out. Urulu sees the pearls and, assuming they're real, says that the lagoon belongs to him. The chieftain threatens to tell Rogers that Binghamton is breaking their treaty if he doesn't cooperate, and Binghamton gives in.
McHale and Parker come out and Urulu explains that he's in business with Binghamton. Parker points out that a combat order can't be evicted without written orders, and Binghamton gladly provides them. McHale tries to explain that the pearls are phony but Binghamton still doesn't believe him. Back at the swamp, McHale tells the crew that Binghamton made their eviction final and Urulu is going to bring in more divers. Virgil is fishing and snags a two-man sub. They open it and discover that it's empty, and McHale gets an idea. He proposes that they turn it into the monster Karatonga and scare off Urulu and his people. McHale puts Parker in command of it.
The next day, Binghamton and Urulu are counting the pearls that the divers bring up. McHale and the crew sneak up and McHale tells them to aim carefully. They fire shots into the air and run out, and point out the sub coming, dressed up as a monster. Urulu and his man panic, even though Binghamton isn't fooled. He stares in horror as Urulu dumps the pearls into the fire as a sacrifice to Karatonga and then runs off. Binghamton tries to put out the fire, just as Parker sets off a smoke grenade inside the sub. He climbs out and accidentally hits a switch, firing a torpedo. The torpedo hits the shore and blows up the pearls, and Binghamton watches his "fortune" go up in smoke.
Later, Rogers gives the crew a citation for capturing the sub. Binghamton summons them and says that they've shattered his dreams and if it wasn't for the citation, he'd throw them in the brig. Urulu arrives and gives Binghamton a bill for $500 for his divers' services, and threatens to send it to Rogers if Binghamton doesn't pay up.
Written by Gadfly on Feb 12, 2017