Garfield is living in a boring, black and white world, claiming that all the color has gone out of his life. He is excited to learn that Jon wants to take him and Odie on vacation, where he imagines himself in places such as Acapulco, Honolulu and Venice, only to be disappointed to find out that they're just going camping.
It takes a while for Garfield to adjust to the great outdoors, immediately taking a dislike to the camp rangers for insulting him at the entrance and misbehaving at the campsite by placing a live fish in a pitcher when asked to collect water by Jon. Jon on the other hand is conversely optimistic about their stay, despite finding out his 'super deluxe' tent has barely enough room to house the three for the week. After nightfall, the trio listen to the radio which is interrupted by news of a panther that has escaped from a zoo lurking in the Lake Woebegone woods area. Right after this news on the radio, the announcer says: "We now return to our regular broadcast of fun music." It then plays very depressing music. Garfield and Odie are terrified and want to leave but Jon assures them that Lake Woebegone is miles from their location. Following the announcement they sing a song (and endure Jon's banjo playing) then go to bed. After they go into their tent, on the hilltops, the panther comes out and growls as it eyes their campsite.
The next day, Odie causes the tent with Jon and Garfield inside to roll into the lake and he then runs off into the nearby woods, which is revealed to be the Lake Woebegone area that the panther is lurking in. The forest rangers are hunting for the panther, and attempt to warn Jon to evacuate, but he is away from the campsite when they arrive so they leave a note. This proves unfortunate as a gust of wind blows the message into a recently extinguished campfire, where it burns up.
After it is revealed that Garfield has eaten all the food for the week, he takes a hike to avoid Jon's ranting and starts to appreciate the beauty of nature, until he meets two forest animals named Dicky Beaver and Billy Bunny who warn Garfield about the escaped panther, claiming it has already attacked other forest animals. Odie appears, after scaring all but Garfield away by accident, and the two eavesdrop on the two rangers passing by with a tranquilizer gun, hoping to capture the panther. The two decide now is the time to collect Jon and leave before they are attacked by the beast and run all the way back to the campsite.
Upon their return, Garfield tries to warn Jon of the danger but Jon insists that there is nothing to worry about and refuses to move while Garfield tries desperately to convince Odie to get into the car. However, during the commotion the full moon comes into view and shines down on the camp to reveal that the panther has now entered their campsite and is approaching the three as they look on in horror. Garfield runs up a tree while Jon and Odie hide in the tent, followed by the car as the panther tears it to shreds and then manages to break into the vehicle by smashing through a window. Scared but unable to watch his family being killed, Garfield leaps from the trees and takes on the panther, clawing at its head and neck but is shaken off. Garfield is in serious danger until the park rangers enter the campsite and subdue the beast with a tranquilizer dart. Jon then says he feels they have had enough adventure and recommends they break camp and return to civilization, much to Garfield's joy. They set off for home with Garfield bragging over how he took on the panther.
