The Baxter family—Catherine Baxter, [Ellie Harvie], Curtis Baxter, [Doug Murray], Finn Baxter, [Christian Martyn], and Alexis Baxter, [Jodelle Ferland]—move from California to Rockland, Maine and settle into their new home during the Christmas season. Finn, a 10-year-old who loves video games, and his older sister Alexis, who spends long hours on her phone and computer, are true technophiles who tend to shut themselves off from their parents. Encouraged by his dad to socialize, Finn befriends their neighbor Mason, [Peter DaCunha], who fills him in on the local legend of a smothered gangster whose ghost haunts the Baxters' house.
While the family is out Christmas shopping, a trio of thieves—Sinclair, [Malcolm McDowell], Jessica, [Debi Mazar], and their new safecracker Hughes, [Eddie Steeples]—break into the house to steal an old Edvard Munch painting valued at $85 million, unaware the home is occupied. They cannot locate the painting in the basement safe. When the Baxters return, the thieves flee, hoping for a quick grab, while Finn and Alexis stay behind due to a tense night of petty family conflicts.
That night, Curtis and Catherine depart for a Christmas party hosted by Catherine's new boss, Mr. Carson, [Ed Asner]. Finn and Alexis remain at home, where Finn discovers a spare controller and, while searching for batteries in the basement, accidentally unlocks a hidden room behind the safe. There, the burglars’ target—the painting known as The Widow—is found, and a frightened Finn bolts while Alexis inadvertently triggers a trap that locks her inside the hidden chamber.
As the snowstorm worsens, the parents are forced to stay at the party, worrying about their kids. Finn scavenges for supplies at a hardware store with only enough money for string, hoping to use improvised tools to help his sister. He also overhears Sinclair and Hughes discussing their plan to break into the house and calls his online friend Simon, [Bill Turnbull], to warn him. Finn sets up a series of booby traps around the house, and the intruders suffer injuries, with Jessica getting tar splashed onto her outfit during one of the close encounters. Eventually Curtis and Catherine manage to return home, and though Simon attempts to help by tracing the kids’ activity through their gamertag and the parents’ credit card details, they don’t trust him and call the police instead.
Back inside, Sinclair and Hughes capture Finn and detain him in their SUV while they try to gain access to the safe. Mason, using quick thinking, hurls snowballs at Jessica, who is left dazed and disheveled, allowing Finn to escape and race back to warn Alexis. Finn frees Alexis and triggers a trap that locks Sinclair and Hughes in the basement, a scene seen by police monitoring the incident on Simon’s TV. Mason completes the takedown by encasing Jessica up to her neck in a headless snowman, prompting the police to rush in and arrest the intruders.
With the criminals in custody, the Baxters are rewarded with four museum passes and $30,000, and Mr. Carson offers a formal apology by way of a plane ticket for Simon to return home and spend Christmas with his family. On Christmas Day, Finn receives a snowboard and an expansion pack for Robo Infantry 3, while Alexis is gifted a tablet. Finn and his dad also get a camping guide, and Finn decides to take a break from video games to go snowboarding with Mason, who has become his new best friend. The final scene shows the offenders’ mugshots being added into a portrait as a quiet, ironic closure to the break-in.
