In the original movie, Kevin is left behind by accident when his family travel to Paris for Christmas. Upon learning that the Wet Bandits, Marv and Harry, intend to rob the McCallister house alongside several other houses in the neighborhood, Kevin defends his house by rigging it with several booby traps that cause some serious injuries to the Wet Bandits, before they capture him, only to be knocked out by his neighbor, Old Man Marley, allowing them to be arrested by the police, due to Marv's stupidity in leaving a calling card behind by leaving the water on in the houses they rob, flooding them as a result. Kate later returns home before the rest of the family to reunite with Kevin, and while Kevin is happy to have his family back, he soon has to deal with his big brother Buzz when the movie ends with Buzz shouting down from upstairs, "Kevin! What did you do to my room?!"
In the sequel, Kevin is upset that the family now intends to celebrate Christmas in Miami, as there are no Christmas trees down there. After Buzz humiliates Kevin during his solo in the school Christmas choir, causing Kevin to retaliate, leading to the performance being ruined, back home, Buzz offers an apology to gain the McCallisters sympathy for what he did, before mocking Kevin over getting the family to sympathize with him, leading to Kevin erupting in anger and telling off the family, refusing to apologize to Buzz, and even insulting his Uncle Frank when he tries to intervene, before storming up to his bed on the third floor to sulk, muttering to himself that his family was nothing but a bunch of jerks. Kate tries to speak to Kevin in private and calm him down, but Kevin is still too livid to be reasoned with, so when Kate mentions that Kevin got his wish last year to be away from his family and might get it again this year, Kevin replies "I hope so!"
When it is discovered that the McCallisters overslept again, they rush to board the airport shuttles and catch their flight, but while Kevin does make it onto the shuttles this time, he is separated from his family at the airport while changing batteries in his Talkboy, mistaking a gentleman wearing a similar coat to Peter as his father, and boards a flight to Manhattan instead of Miami. When the McCallisters discover Kevin is not with them in Miami, Peter is furious, while Kate faints when the truth sinks in that Kevin was left behind again. Speaking with the Miami police, they learn that Kevin does have Peter's bag with his credit card in it, so they can track Kevin when he uses it. Meanwhile, when Kevin realizes he's alone in New York while his family is in Miami, he decides to use that to his advantage and enjoy Manhattan, visiting the World Trade Center's Twin Towers and checking into the Plaza Hotel using Peter's credit card and a fake recording of Peter's voice to make a reservation. However, the hotel concierge, Mr. Hector, is suspicious of Kevin, and while Kevin is out exploring the city and visiting Duncan's Toy Chest, Mr. Hector discovers the stolen credit card, so when Kevin returns to the Plaza asking for help after having a run-in with his old enemies, the Wet Bandits, Mr. Hector intends to turn Kevin over to the NYPD for the stolen credit card, but Kevin outwits him and his staff and escapes, only to be captured by the Wet Bandits, who take Kevin to Central Park as they reveal their plans to rob Duncan's Toy Chest, unaware of Kevin recording their confession of their plan, before causing a distraction that allows him to escape them for the time being. When the McCallisters arrive in Manhattan and check into the Plaza, Mr. Hector and his staff try to apologize for their actions, but the McCallisters will have none of it. Mr. Hector offers them a complimentary suite as an apology, but Kate still shows how upset she is with him when she slaps him in anger over trying to talk her out of going after Kevin alone, leaving Mr. Hector humbled and trying not to cry from the pain.
Kevin, meanwhile, befriends the pigeon lady he saw in Central Park previously when she frees his trapped foot after it was stuck between some rocks. Taking Kevin back to her loft above Carnegie Hall, she explains how her life has fallen apart, and Kevin offers to be her friend to help her rebuild it. Later, as Kevin heads out, he passes the Beth Israel Children's Hospital, and after waving hello to one of the ill children watching him from their window, remembering what Mr. Duncan said about the money he was collecting going to the Children's Hospital and the Wet Bandits' intent to steal it, Kevin declares, "You can mess with a lot of things, but you don't mess with kids on Christmas", and decides to stop the Wet Bandits himself. After rigging his Uncle Rob's house that was undergoing renovations with booby traps, Kevin heads to Duncan's Toy Chest, catching the Wet Bandits in the middle of their robbery and triggering the store's alarm by breaking the window with a brick carrying a note to Mr. Duncan attached to it, leading the Wet Bandits to chase him back to Rob's house to suffer a ton of pain and humiliation from the traps before Kevin flees to Central Park, stopping by a phone to call the NYPD. However, as Kevin tries to enter the park, he slips on a patch of ice, allowing the Wet Bandits to capture him. Taking him into the park, they confiscate the evidence against them, before Harry pulls out a revolver, intending to kill Kevin in revenge for all the suffering he's put them through. However, before he can pull the trigger, the pigeon lady Kevin befriended appears and provides a distraction to give Kevin a chance to escape before she covers the Wet Bandits in bird seed, leaving them at the mercy of the pigeons as they swarm the crooks and pin them to the ground, giving Kevin time to set off his signal to the NYPD, leading to the Wet Bandits being arrested once more, this time with enough evidence against them to put them away for good.
Kevin later travels to Rockefeller Center to look at the large Christmas tree there, where he makes a request to God to be with his family again, even offering an apology for all the trouble he's put them through. That's when he is reunited with Kate, and they return to the Plaza together to reunite with the rest of the McCallisters, waking up to find that Mr. Duncan, in gratitude for saving the donation money, has delivered a huge load of presents to the Plaza to thank Kevin and ensure his family has a Merry Christmas. Buzz even offers a sincere apology this time to Kevin for before with the Christmas choir incident, and as the McCallisters celebrate, Kevin heads down to Central Park to give one of the ceramic turtle doves Mr. Duncan gave him earlier to the pigeon lady as a sign of friendship. However, Kevin's heartwarming moment with the pigeon lady is ruined when Buzz receives the hotel bill from Kevin's earlier stay and shows it to Peter, causing him to scream in fury, "Kevin! You spent $967 on room service?!" Busted, Kevin flees back to the Plaza to face his irate father.