AHe doesn't. There's never a moment when he's left home alone, even when Peter and Natalie go to the airport to pick up the Royal Family. There's always the butler Prescott (Erick Avari) or the maid Molly (Barbara Babcock) with him. "Home alone" in this movie seems to translate as having to protect the house by himself because no one will believe Kevin's contention that there are burglars afoot.
AThe first three movies in the Home Alone series -- Home Alone (1990), Home Alone 2: Lost in New York (1992), and Home Alone 3 (1997) -- were all based on screenplays by writer and producer John Hughes. The screenplay for Home Alone 4 was co-written by screenwriters Debra Frank and Steve Hayes. The first three movies have been novelized by Todd Strasser, but fourth movie has not. A fifth movie in the series, Home Alone: The Holiday Heist, was released in 2012.
AMolly locks Kevin in the wine cellar with Prescott, but Prescott remembers the dumb waiter and sends Kevin up in it. The dumb waiter traps Marv's head, but Vera frees him. Kevin hits them both with a soup pot. Molly goes after Kevin with a frying pan, but Kevin traps her in the elevator. Meanwhile at the airport, Natalie and Peter arrive to pick up the Royal Family, but Peter decides to go back home to check on Kevin. Kate has the same idea, and she drives over with Buzz and Megan. Back at Natalie's house, Marv goes looking for Kevin in the bedroom, but Kevin has set up another trap that results in a chest of drawers falling on him. When Kevin plays a recording that he spliced together of Marv telling Vera to shut up, Vera gets angry and slaps Marv. After a series of mishaps befall Marv and Vera, such as falling down the stairs, spinning around on a revolving bar, and falling from a chandelier, Molly gets out of the elevator and is just about to hit Kevin with the frying pan when Prescott, having escaped from the wine cellar, hits her first. Just then, Peter and Kate drive up, so Marv and Vera run for the back door, but Buzz and Megan trip them and they rush out. Peter hugs Kevin and apologizes for not believing him. Prescott calls the police. As Natalie and the Royal family drive home, the police speed past them. They haul Marv, Vera, and Molly away. Prescott quits his job. Peter breaks up with Natalie and goes back to Kate. Kevin invites the Royal Family to spend Christmas with the McCallisters. Natalie starts to hyperventilate. In the final scene, everyone hugs everyone while Natalie is left alone breathing into a paper bag.