Jon, Garfield and Odie check out the Food Monster, a new supermarket with numerous deals. None of the customers there are aware of the store's true nature.
On the way home, Garfield, Jon and Odie stop by Gramps' supermarket to pick up some shopping supplies. When they enter, they find the place low on customers. Gramps tells them that the new Food Monster Supermarket is taking his customers. Mr. Baggett, the owner of the Food Monster, then arrives, hoping Gramps will sell his market in order to add more parking spaces. Noticing Jon, Baggett lures him into the Food Monster with promising deals, much to Gramps' dismay.
After entering the Food Monster, Jon shops while Garfield goes over his shopping list. While looking forward to driving Gramps out of business, Mr. Baggett makes sure that the store is set to force customers into making more expensive purchases. While shopping, Jon sends Odie to fetch a pound of flour. Although Jon acknowledges the higher food prices, he is still satisfied with the multiple deals.
After Mr. Baggett makes a new special, one of his employees informs him about Odie in one of the aisles. Thinking he could cause trouble, Baggett goes to investigate. When he finds Odie, Baguette demands that he come down, which eventually leads to a chase. As Jon and Garfield continue to shop, they spot Odie being chased by Baggett. Garfield jumps into another cart to rescue Odie from Baggett. The three go through numerous aisles, leaving messes along the way. They eventually go through the fruit aisle, where Garfield and Odie eat bananas and throw the peels on the floor to trip Baggett. Trying to get out, Garfield uses the Express Lane to escape; Baggett manages to catch up and capture them.
When Jon arrives, Mr. Baggett demands that he pay for the damages caused by his pets. Jon tells him that his prices are too high, to which Baggett noting that his store is successful as his customers are gullible enough to pay for them. As Baggett talks about doing away with Gramps' store, Garfield holds up a microphone to his mouth, allowing other customers to overhear his scheme. When they hear how the food at Gramps' is cheaper and superior, the customers leave the Food Monster, much to Baggett's shock.
Meanwhile, Gramps prepares to shut down his store, when he sees a long line of customers ready to enter his store. Garfield, Jon and Odie arrive as well, with Jon declaring that Garfield is primarily responsible for saving Gramps' store. Mr. Baggett tries in vain to get the customers back by offering more deals. Gramps rewards Garfield by letting him have anything at his store for free. Garfield proceeds to fill up a cart with much of the store's contents, compelling Gramps to reconsider his decision.