The Planet Express crew are watching television when an advertisement for Slurm comes on. The ad announces the beginning of a contest: whoever finds a golden bottlecap inside a can of Slurm wins a free trip to the Slurm bottling plant on Planet Wormulon, as well as a party with Slurm mascot Slurms MacKenzie. Fry resolves to find the bottle cap by drinking massive quantities of Slurm.
Bender walks in feeling ill, and Professor Farnsworth uses it as an excuse to test his experimental F-ray, a device that enables people to look inside anything. He shines it at Bender and finds that Amy's watch (which Bender had stolen) was causing the problem. After removing the watch, the professor gives the F-ray to Fry and Bender to put away; instead, they decide to have some fun with it. Bender shines it on Fry, which may make him infertile or cause genetic defects in his children as Fry initially cries "Ow, my sperm!" but feels nothing when Bender shines it on him for a second time. After trying the F-ray out on random objects, Fry eventually realizes that they could use the F-ray to scan Slurm cans for the golden bottle cap. After checking thousands of cans, they give up on finding the winning can, and return to the laboratory with the F-ray. Fry settles in to relax with a can of Slurm from the refrigerator, and ends up choking on a bottle cap that was in it.
The Planet Express crew arrives at Slurm Centralized Industrial Fabrication Unit and are greeted by Glurmo. The crew takes a riverboat tour down a river of Slurm through the factory, and see the Grunka-Lunkas sing their song. Overwhelmed with thirst, Fry tries to drink from the river (not realizing that it's not in fact Slurm), and falls in. Leela dives in to save him, and Bender joins them for no good reason. The three are sucked into a whirlpool and deposited in a cave under the factory.
Under the factory, they discover that the factory they toured was a fake. Making their way through the tunnels, they enter the real factory and discover Slurm's true nature: it is a secretion from the rear orifice of a giant worm, the Slurm Queen. They are discovered and captured by the worms. The three are placed into overly complicated death traps and left unguarded. They escape, but are pursued by the Slurm Queen. Slurms MacKenzie, exhausted from his years of partying, arrives and sacrifices himself to save Fry, Leela, and Bender.
When they escape, the Slurm Queen bemoans that the company is ruined, and disgustingly drinks her own Slurm, direct from the source, as a comfort. However, Fry is so addicted to Slurm that he keeps the nature of Slurm a secret so that it can continue to be produced.