To make up for a food fight that disrupted a high school Christmas bake sale before Anna's bachelorette party, Kevin joins Harper, Lily, and their friends to help with a new one at Sunset Ridge High School. Kevin reminds everyone, “The best prize that life can offer is working hard at work worth doing.”
However, the festive mood is shattered on Christmas Eve when the Wet/Sticky Bandits, Harry and Marv, arrive in Los Angeles after escaping from another prison riot. They plan to rob a charity store, but Kevin spots them and manages to escape. He finds an abandoned hotel and recruits Harper, Lily, and their friends to help set traps. After setting the traps, they go to the charity store to confront Harry and Marv. Kevin puts marbles on the pavement, and as the bandits chase him and the teens, they slip and fall hard. They lead the bandits to the hotel, where the duo falls victim to the elaborate traps once again.
After the bandits have endured all of the traps, Kevin escapes the hotel and leads Harry and Marv on a chase to Echo Park. He draws them away from the teens, demonstrating loyalty and selflessness. Cornering Kevin, the bandits are ready to end him for good when police arrive, alerted by Harper and her friends with evidence of the robbery. Harry and Marv are arrested, and Kevin is reunited with his new friends.