SpongeBob has to carry an extremely heavy bag of Gary's snail food back to his pineapple home. Patrick interrupts him, insisting that he has something important to share, but he cannot tell SpongeBob yet. SpongeBob then sees a package near his front door: it is a new Mermaid Man and Barnacle Boy paddleball set, on which he will train like crazy to beat the record of the Dirty Bubble (the Dirty Bubble Challenge). This is, however, an impressive 29,998,559,671,349 hits in a row on the paddleball, which SpongeBob cannot do even after many, many attempts.
SpongeBob is at the game for a long time, and forgets to feed Gary, who runs away from home and lands in the big city of Bass Vegas. There he flees from stray snails, who just wanted to invite him to lunch but seem menacing. Gary is later taken in by an old lady, who calls him "Miss Tuftsy", likely the name of an old snail who the lady has lost. With her, Gary gets everything he has ever dreamed of: biscuits, cakes and other food until the moment of the departure. SpongeBob, however, is missing something and does not know it yet.
Meanwhile in Bikini Bottom, SpongeBob has played paddleball for 6-7 days without success and is in his bedroom. Patrick enters the house and finds it destroyed-looking and heads to SpongeBob. He finds SB lying on the ground. Patrick laments to SpongeBob about the Dirty Bubble Challenge, confessing that he once beat the challenge many years ago and won the trophy. He is sad, though, as he lost the trophy. After Patrick drinks a glass of expired seahorse milk, they both realize that Gary is not there. SpongeBob is depressed and tries to find his snail again.
SpongeBob distributes flyers, buys advertising space and calls for his pet, but everything is unsuccessful. Still in the old lady's house, Gary is given a large amount of fliers as a litterbox, only to notice that these fliers are SpongeBob's notices, trying to get Gary to come home. Gary then finds numerous empty snail shells in a cupboard, which suggests to him that the woman fattens up her snails and then eats them. Gary then sees a scary picture of the lady with her old snails. Gary flees the house, but is pursued by the grandma, who flings cookies at him reminiscent of a horror villain. SpongeBob and Gary meet again and SpongeBob promises to take much better care of his small pet from now on.