Jon and his pets go visit a haunted house called "Mystic Manor", only to find that it has been closed for years. As Jon takes a nap in a motel, Odie wanders into the manor before Garfield goes in to save him.
Jon tries to take Garfield and Odie to Mystic Manor, a haunted house. However, the owner of the house informs them that it has been closed for years (as tourists went in, "they just didn't come out"). Jon then decides to check into a nearby motel.
As Jon is about to take a nap before preparing dinner, he tells Garfield to make sure Odie remains safe, or the fat cat will get no dinner. As Garfield falls asleep, Odie goes after a bat, which leads him into Mystic Manor through a hole. Garfield reluctantly follows him, which brings him into the garden of Mystic Manor. After pulling a rope (with a sign that says "DO NOT PULL ROPE"), he falls down a shaft into the house.
Inside, Garfield encounters unusual aspects of the house, such as a trick mirror, an ad-libbing echo, cameo guest stars, and an elevator door that leads to a stairway. He is also chased by a monster. Eventually he finds and reunites with Odie. The two then exit the house by crashing through a wall (which Garfield calls playing "instant door") and rush into Jon.
When they inform him of their visit to Mystic Manor, Jon tries to bring them to Mystic Manor to show them that they should not be afraid of it. Upon their arrival, they instead find a skyscraper under construction. A construction worker tells them that Mystic Manor was demolished a few years ago. Terrified, the trio race to the car and drive off.
The construction worker then turns out to be the owner in disguise. The owner then laughs, noting "That's the ninth one this week and it's only Tuesday". He continues laughing as he heads back to the actual Mystic Manor.
- Mystic Manor Owner (voiced by Gregg Berger)
- Nancy Ritz (cameo)
- Sluggo Smith (cameo)
- Surfer (voiced by Gregg Berger)
- Orson Pig (cameo)
- Wade Duck (cameo)
- Roy Rooster (cameo)
- Jim Davis (cameo)
- When Garfield slides down a pole, he passes by three rooms. They include a herd of elephants, the U.S. Acres farm and Jim Davis (with his head on Garfield's body) drawing a picture of Garfield respectively.
- Garfield mentions Tarzan when he enters the garden of Mystic Manor.
- The monster that goes after Garfield resembles Frankenstein's monster.
- At one point, Garfield encounters Nancy Ritz and Sluggo Smith from the comic strip Nancy.