The book opens with a ping pong game. At one point protagonist Joe Burton serves the ping pong ball by kicking it instead of using the paddle, much to his older sister Mindy's chagrin. He then follows that by telling her there's a spider on her back. Joe reveals that he doesn't look like anyone else in the family. They're all tall and skinny and he's short and stout.
Shortly after arriving in the rec room, Joe's friend Moose sits on Joe's chest. Moose lives next door. His father, Mr. McCall, and Joe's father have a running rivalry involving the produce they grow in their gardens.
Mr. McCall has it out for Joe's dog Buster, as the mutt has an affinity for trampling into the McCall's garden and digging it up. Buster is revealed to be digging up the McCall's garden. Mr. McCall comes out in a rampage and threatens the children and their dog. Joe pulls out his trusty dog whistle and Buster slinks back into the Burton's yard. Joe's dad thinks it would be a fine time to visit the little old lady down the block, as she sells gardening supplies from the first floor of her three story house. The woman, Lilah stays in business selling lots of garden-related paraphernalia.
Joe's dad loves lawn ornaments, even going so far as to dress-up the plaster deer and flamingos on his lawn for the holidays. Joe's mother however hates the lawn ornaments and finds them embarrassing.
Joe's dad spies two darling little lawn gnomes and instantly purchases the small plaster men. Mindy warns that the lawn gnomes look evil. Joe's father however ignores such frightful talk and cheerfully names the little guys Chip (because his tooth is chipped) and Hap (because he's so happy looking).
Walking back home with the gnomes in hand, Joe thinks he sees Hap change its expression from a cheery grin to a grim scowl.
Strange horrible things start to happen to Mr. McCall's lawn, and Buster the dog keeps getting blamed. The suspicion quickly turns from the dog to Joe when Mr. McCall awakes one morning to find someone has drawn smiley faces on his prized casaba melons. Joe is immediately suspected of the deed. Joe pleads his innocence and even brings in evidence of the real perpetrators: there's black paint underneath one of the gnome's hands and a melon seed between his lips. It soon becomes apparent that the rivalry between the neighboring gardening aficionados is escalating.
Joe becomes convinced that the gnomes are responsible and talks Moose into staking out the two houses to catch the lawn ornaments in the act. The two hide across the street on a stakeout. Eventually, the gnomes do come to life and start their terrorizing. The giggling men start splashing big buckets of paint against the exterior of Joe's house. A confrontation between the gnomes and the children breaks out and at some point Mindy shows up and one of the gnomes drags her into the street by her hair.
The gnomes suddenly get very serious and reveal that they are Mischief Gnomes who were kidnapped from their native forest and sold into slavery. The gnomes reveal that they can't help causing trouble, it's in their nature. If the three kids will help rescue their friends being held at the garden supply store, Chip and Hap promise to leave forever. The kids agree and make their way to the old woman's house.
The other kidnapped ornaments are supposedly in Lilah's basement. Hap and Chip would have freed them alone but they weren't able to get in the basement window. Now with the help of the children, they'll be able to free their six gnome friends. The kids lower the gnomes into the dark basement and follow behind. Once inside, they see that they've been tricked. There's not six other gnomes. There's six hundred.
The hordes of gnomes come to life and start attacking the children. Some want to tickle an unwilling Mindy. Other gnomes want to use the children as trampolines or play tug of war with their bodies. The children are upset about being tricked.
Luckily, Joe remembers how gnomes are scared of dogs and so he calls for Buster to come into the basement using his whistle. But it turns out gnomes aren't scared of dogs; they're scared of dog whistles. All of the gnomes freeze into place as soon as Joe blows the trinket.
Joe's dad, distraught from mysteriously losing his two lawn gnomes, brings home an eight foot tall plaster gorilla for the garden. Joe says "I think it's a beauty, Dad. It's the best looking lawn gorilla I ever saw." Joe somehow tells the gorilla not to cause trouble like the lawn gnomes did, then the gorilla winks.
Television adaptation
The episode's ending is more different than in the book. The lawn gnomes do not get destroyed, but instead attack Major McCall turning him into a lawn ornament, who is found by Joe and his family and the judges.
TV episode Trivia
On this episodes theme, the dog's eyes do not light up.
This is the last of 3 episodes on the DVD, Go Eat Worms.
This episode was adapted into Goosebumps Presents Book #18, the final book in the series.