Once again, the McCallister family is preparing for a Christmas vacation. This time they're heading the snowless summer spot of Miami, Florida. Kevin expresses his dislike for snowlike summer spots as Christmas vacation spots, because of what he sees as a lack of snow and Christmas trees in places like Miami. During a Christmas concert with all the kids, Buzz humiliates Kevin by putting Christmas candle-shaped lights behind Kevin's ears, making them glow, and then as drum sticks. This causes Kevin to push Buzz who in the process pushes others with him as well as them pushing others as well, causing all the kids except for Kevin to fall the stage, and the cardboard Christmas tree to fall on the pianist making her fall as well. Though Buzz apologizes to both Kevin and to their family, Kevin, knowing that Buzz was faking it and sucking up to the family, does not apologize, claiming his stunt against Buzz was justified by Buzz's constant harrassment. He then heads up to the third floor again by himself, reiterating his disgust for the family's decision to go to Miami, and wishing he had his own money so he could go on his own vacation by himself. When his mother Kate reminds him that he got his wish to be home alone last time and that maybe he'll get his wish to go on his own vacation this time, he angrily tells her, "I hope so!"
During the night a storm once again occurs, but the family oversleeps, due to Kevin's dad accidentally unplugging the alarm clock to while looking for his charger the night before. Once again the family rushes to the airport, but this time, Kevin comes along. But it's when Kevin is distracted trying to replace old batteries with new batteries into his Talkboy toy that he becomes separated with his family. Kevin sees a man who from behind looks exactly like his dad Peter, and follows him. While his family boards the flight to Miami, he accidentally follows the "Peter Look-Alike" onto a flight going to New York.
In Miami, when the family is gathering together and getting bags, they finally notice that Kevin's luggage is there but that Kevin is not with them. When Kate notices, she at first laughs about it, but then yells out, "KEVIN!" and promptly faints.
Meanwhile, in New York, Kevin realizes that he's in the wrong place; but instead of being scared, he sees it as an adventure. He explores all around New York City, visiting the biggest buildings and checking into the Plaza Hotel, which he had heard about on a TV game show the night before (the night of the concert). Though he made a convincing story that he's with his father on a business trip, the staff of concierge Mr. Hector, bellhop Cedric and front desk worker Ms. Stone are suspicious of the lone boy. Back in Miami, Kevin's parents have contacted the police about their situation. After realizing Kevin has Peter's father's bag, which contains his wallet, they find out that they can reach him by checking his credit card activity. At the same time the credit card is being mentioned, Kevin is using the card to check in the hotel. That evening, Kevin swims in the pool, only to find out that his father's shorts are too big for him. He uses room service to get a bowl of ice cream and other junk while watching a sequel to the movie he saw in the original film,meventually scaring him. That night Mr. Hector tries to check up on Kevin. Kevin uses his Talkboy containing the voice of Uncle Frank from a recording earlier in the movie to scare him off. Before going to bed, Kevin looks through his father's address book and learns that his Uncle Rob has a vacant renovated apartment close by.
The next morning, the Plaza Hotel presents Kevin with a limo and cheese pizza as an apology for Mr. Hector's behavior from the night before. Kevin is taken to Duncan's Toy Chest where he meets and becomes friends with, the store owner Mr. Duncan. Meanwhile, planning on robbing the store are Harry and Marv, who travel to New York as well via fish truck, having escaped from a prison in Chicago during a riot and continue their stealing ways by changing their nickname from the "Wet Bandits" to the "Sticky Bandits" after stealing money from a Santa Claus with duct tape. Marv shows off the new nickname by using double-sided masking tape to steal 14 cents from a Santa Claus' donation kettle on the street, which Harry doesn't find funny. Outside the store Harry and Marv reunite with Kevin, who scares them off with a scream and a chase. Kevin hopes to find safety from Mr. Hector, but earlier Mr. Hector discovered the credit card was "stolen". When Kevin sees that he has no way out, he runs from Hector inside the hotel. Also chasing him along with Hector is Cedric and Ms. Stone. They chase all the way to his room with a police officer named Cliff and a security guard. Using the movie he watched the other night, Kevin once again is able to scare them off, by using one character's lines and pausing out the others' (as he did with the pizza guy and Marv in the original film). While the staff slowly crawls their way out of the room, Mr. Hector warns other guests to "Stay in your rooms! This is an emergency! There's an insane guest with a gun!" Though Kevin escapes from the Hotel Staff through and emergency exit, he is recaptured by Harry and Marv. They plan to get their revenge on Kevin for sending them to prison in the original film. Marv slips to Kevin about their plan to heist on Duncan's Toy Chest, unaware that Kevin is recording the plans on his Talkboy. Kevin eventually escapes from the burglars by hiding in a hansom cab.
In Miami, where Kevin's family is staying in a motel that forces them to share one room, they are informed on the whereabouts of Kevin, and they pack up to go to New York. When they get to the Plaza, they confront the hotel staff for letting Kevin check into a hotel alone in the first place and then letting him escape. Kate then decides to search for Kevin against the advice of Peter and the staff, while the rest of the family and their luggage are taken up to a complimentary suite provided by Mr. Hector. At Central Park Kevin meets the Pigeon Lady, a homeless woman who has pigeons all around her. She takes him to the basement of a concert arena (Carnegie Hall) where she lives. The two tell each other about their issues and find ways to make things better. While looking up at a kid in a hospital window with compassion and responding in kind to the kid's wave by waving right back, Kevin decides there's only one thing he can do: Stop the burglars from robbing the toy store. He sets up his Uncle's vacant renovated apartment for the booby traps, then arrives at the toy store just in time to see them taking the cash that is supposed to go to the children's hospital. He then takes two photographs of them and then throws a rock tied with a note to Mr. Duncan through the store window, shattering it and setting off the store's burglar alarm. Kevin continues to track down the two criminals and leads them to the traps. After the traps are pulled, Kevin slips on a patch of ice while escaping and is eventually captured by the crooks, who take him to Central Park to kill him; but once again, Kevin's new ally (Pigeon Lady) comes to the rescue by throwing bird seed on Harry and Marv, causing the birds to attack the two. After the two are arrested, the police come upon Kevin's photos and tape and plan to use them as evidence against the pair. Back at Duncan's Toy Shop, the police inform Mr. Duncan about the apprenhension of the two criminals and he reads the note from the rock Kevin used to foil the robbery. In Times Square, Kate comes across two police officers who question her about Kevin's whereabouts. She then remembers Kevin's fondness of Christmas trees and deduces that he must be at Rockefeller Center, so she asks them to take her there. After reuniting with Kate at the Rockefeller Center Christmas Tree, Kevin reunites with the rest of his family and they stay at the Plaza Hotel. As a thank you to Kevin for saving his shop, Mr. Duncan sends free gifts to Kevin and his family, and Buzz says that had it not been for Kevin getting on the wrong flight, they wouldn't be in the complimentary suite with the Christmas tree and gifts in the first place; thus he allows Kevin to open up the first present as a sign of reconciliation. While his family opens presents, Kevin visits the Pigeon Lady right outside. He gives her a turtle dove (2 that were given to him earlier by Mr. Duncan). He promises her that he'll never forget her and that he'll aways be her friend. Meanwhile, Buzz receives Kevin's room service bill and then shows it to Peter, who then calls out, "Kevin! You spent $967 on room service?!" Upon hearing that, Kevin heads back to the hotel, and the film ends.
Kevin McCallister (Macaulay Culkin)
Harry Lime (Joe Pesci)
Marv Merchants (Daniel Stern)
Kate McCallister (Catherine O'Hara)
Peter McCallister (John Heard)
Pigeon Lady (Brenda Fricker)
Mr. Hector (Tim Curry)
Cedric (Rob Schnieder)