The illustration on the cover shows a Camp Jellyjam counselor with a strange, wide grin on his face.
Wendy and her younger brother, Elliot are on a road trip with their parents, which Elliot hates because he wanted to go to summer camp. The Wyoming countryside does very little to excite the two kids, so Wendy suggests that maybe she and Elliot could ride in the trailer hitched behind their car. Once inside the trailer, the two kids merrily pass the time as the trailer accelerates down the highway. When the ride gets a little bumpy, the kids assume their mother is driving, but the trailer hitch soon breaks, sending the two kids off the road and tumbling down a hill and crashes (despite this, Wendy and Elliot do not suffer any injuries).
Wendy opens the trailer door when she hears someone knocking, assuming her parents are on the other side. Instead, it's a blond man dressed in white. The man introduces himself as Buddy, one of the counselors of a sports camp called King Jellyjam's Sports Camp. Elliot is excited that he finally gets to go to camp, but Wendy is more concerned about contacting her parents. Buddy lets Elliot and Wendy stay until they can make contact with the authorities. While Elliot makes himself at home, competing with the campers for King Coins (six of which earns campers the right to participate in a ceremony called The Winners' Walk), Wendy is lectured by her counselor, Holly, for not living by the camp slogan, "Only The Best." Things get weirder when one of Wendy's camp buddies, Diedre, participates in the Winners' Walk after winning her sixth King Coin, and doesn't come back.
Wendy and her two other camp buddies, Ivy and Jan, break curfew to look for their friend. A little girl named Alicia (who appeared earlier in the story to warn Wendy away from the camp) appears again to warn Wendy, Ivy, and Jan about the camp. This time, she tells them that she followed the counselors and discovered something horrible. The three run back to their dorms -- and find Deidre's belongings missing. The next day, Wendy confronts Buddy about Deidre's disappearance and Alicia's warnings. Buddy tells Wendy that Deidre left the camp on her own accord and that King Jellyjam's Sports Camp has never had a girl named Alicia. Wendy tries to call her parents, but the pay phones are disconnected. Buddy approaches Wendy (after spying on her attempts at calling home) and gives her an itinerary of sports she must complete before the end of the day.
First, Wendy loses her tennis match against an African-American girl who wins her sixth King Coin. After tennis, Wendy is hustled down to the softball diamond. She practices her swings with the bat and accidentally slams the bat into Buddy's chest. Despite the sickening "eggs breaking" sound it makes against his chest, Buddy does not feel any pain from getting hit and cheerfully recommends that Wendy try a lighter bat. After another Winners' Walk ceremony (and another revelation that the winners have disappeared), Wendy begs Elliot to escape the camp with her. However, Elliot is in no rush; he's already on his fifth King Coin and is prepped to win his sixth. That night, Wendy follows the camp counselors into the woods to investigate these weird events. Wendy covertly follows the counselors into a small theater. Wendy ducks into a broom closet and watches as Buddy hypnotizes the rest of the counselors and himself (the nightly hypnotizing explains why Buddy didn't react to the pain of getting hit with the bat and why the other counselors are perpetually cheerful). He tells the counselors that they must always serve The Master.
Before Wendy can figure out who "The Master" is, she draws attention to herself by sneezing. Panicked over the prospect of getting caught, Wendy escapes down a passageway leading to the basement. As Wendy makes her way down, a rank odor fills the air. Once below the ground, Wendy sees dozens of kids working hard. All of the Winners' Walk champions and Alicia are moving furiously with mops and hoses around an enormous purple gelatinous creature wearing a gold crown and sweating snails on the children trying to clean him. Wendy spots a sobbing Deidre and rushes to her side. Deidre explains that the camp counselors are pushing the kids in sports because "Only The Best" are chosen to be King Jellyjam's slaves. The creature can't stand his own stench so he needs the most athletic beings to keep him clean. Anyone who stops or screws up in cleaning King Jellyjam gets eaten and his belches are the source of Camp Jellyjam's constant earthquakes. Wendy escapes the theater and falls asleep in the woods.
Wendy is awakened the next day by the starting whistle of a track meet. Wendy suddenly remembers that Elliot is participating in the track meet so he can win his sixth King Coin. Wendy tries to whistle to get her brother's attention, but her mouth is too dry. Wendy then races to up to her brother and tackles him to the ground just as he approaches the finish line. Elliot is momentarily angry, but agrees to follow her back to the theater in the clearing to see the monster for himself. Once beneath the ground again, Wendy reveals to Elliot that she has a plan to defeat King Jellyjam. She orders all the children to lie on the ground and stay still. King Jellyjam wails and attempts to grab the slaves, but can't because of its thick, disgusting fingers. Wendy is then grabbed by King Jellyjam (since she's the only one who didn't lie on the ground with the rest of the children) and is about to be eaten, but, without the kids there to wash him, King Jellyjam melts into a pile of his own rancid, purple goo.
Wendy, Elliot, and the freed child slaves rush out of the igloo, but are stopped by the band of brainwashed counselors. Just as they are about to attack, the police arrive to investigate the source of the campground's stench (which has been plaguing the people living by it for quite some time). Wendy and Elliot are soon reunited with their parents. Two weeks after the events of the camp, Buddy (now rehabilitated) stops by the house to award Elliot his sixth King Coin. Just as Elliot is about to take it, a horrible stench fills the room. Wendy panics, but it's revealed that the stench is just Wendy's mother cooking brussel sprouts.
Cover Art Gallery
This book was made into a Goosebumps Graphix story in the Scary Summer book, drawn by Kyle Baker.