On December 23, Lincoln Loud receives a package from the Snail Shipping postal service. Inside the package is a present he spent the whole year saving up to buy before he could give it to his entire family as a Christmas gift: a sled that can support thirteen people. Suddenly, his father calls everybody to come to eat breakfast. During breakfast, Rita, the mother of the family, receives a phone call from her oldest daughter, Lori. During the phone call, Lori tells everyone that she may not be able to come home for Christmas that year because she needs to study for her upcoming exams and prepare for an upcoming golf tournament. Not only that, but the Loud family's house is three hours away from her college, and she thinks it may be easier to spend Christmas with her boyfriend, Bobby, because he lives closer to campus. Soon after that, Luna reveals that her girlfriend, Sam, invited her to come skiing with her on Christmas Day, and Luan reveals that she has a comedy gig at the local senior center, Sunset Canyon Retirement Home. Everybody supports their plans for the holiday, except for Lincoln, because them being away would interfere with his plan to use the sled that he worked hard to buy all year, and he does not want his present for the family to go to waste immediately. He throws his mother's cell phone into a glass of orange juice, which prompts her to hold a family meeting. At the family meeting, the parents announce that they are taking the kids who do not have holiday plans with them on a vacation to Miami. Lincoln protests against the trip, as he will definitely not be able to use his sled in Miami, but he also justifies that his youngest sister, Lily, has been selected to light the Christmas tree at the mall on Christmas Eve. Although the parents understand the sources of Lincoln's conservative attitude, they encourage him to play along with them and make the most of the current situation. Lincoln then tries to appeal to his family one last time by revealing his present to them all, but since he has not handled the package with the sled inside cautiously, the sled is broken to pieces by the time he opens the package. Because the sled is broken to pieces, along with the fact that there has not been any snowfall recently, the parents make the final decision to take the entire family to Miami. Lincoln is devastated by this decision because he wants to preserve his family traditions, and he decides to bring everyone together for the holidays once and for all. He enlists help from his best friend, Clyde, who agrees to assist him in his scheme. They decide to start by making Lori homesick so she will come home for the holidays. Lincoln mails his father's figgy pudding to Lori's college, and when it arrives the next day, Lori becomes homesick because she has never missed her father's figgy pudding on Christmas once. She then decides to come home for the holidays, and after telling her boyfriend, Bobby, about her plan, he starts to drive her home on his moped. Next up, the boys take voice recordings from a rock star named Mick Swagger, then mix them up to present a fake message that he will be arriving in their town on Christmas Day. They then send the message to Luna, who falls for it and decides to attend Mick Swagger's "concert" on that day, knowing that it is a once-in-a-lifetime opportunity. Next up, they decide that they need to create some kind of threat that would scare the Loud parents into not wanting to go to Miami. They use Clyde's theater props and tandem bicycle to create a shark/crocodile hybrid called a "Sharkodile" that they deem to be so dangerous, nobody will be safe on land or in the water. They then steal a mannequin named Tanya from the mall to use as a victim in the staged attack they plan to film. Next up, they go to the senior center and dirty Luan's reputation until the board decides to fire her from her gig. With Lincoln's sisters who had plans taken care of, he and Clyde take their "Sharkodile" and mannequin to the lake, which they stage as Miami Beach, then film an alleged Sharkodile attack. They then send it to the local news reporter, Katherine Mulligan, who believes the footage to be real and warns everybody over a news broadcast not to go to Miami anytime soon because of the dangerous beast lurking there. The Loud family is among the people who watch the news broadcast, and the parents declare that despite the Sharkodile leading them to cancel their plans to go to Miami, they can still make the most of the situation by attending the tree-lighting ceremony at the mall that night. Meanwhile, Bobby's moped runs out of gas, leaving him and Lori stranded on the highway until further notice. Back at the Loud house, Lincoln has gotten dressed for the tree-lighting ceremony, but notices that many of his sisters are let down; Leni is upset because her boss fired her from her job at the mall because she "lost" the mannequin that Lincoln and Clyde stole and could not recover it, Luna is upset because Sam broke up with her as a result of her deciding to attend Mick Swagger's alleged concert instead of going skiing with her, Luan is disappointed because she got fired from her comedy gig, and everyone else is disappointed because they had plans for when they arrived in Miami. Suddenly, Lisa presents a Sharkodile-tranquilizing spray that she had just created as a means of hopefully protecting everyone from the beast. Concerned that it may not be safe, Lincoln tries to snatch it from her, but he accidentally sprays some of the spray into his father's eyes, which causes him to act insane before passing out. Suddenly, Rita gets a call from Lori about her being stuck on the highway with no working mode of transportation to head home, which prompts her to leave and pick up her oldest daughter before she and Bobby freeze to death. Suddenly, Lincoln gets a call from Clyde that tells him to turn on the news. During the news broadcast, he hears that the entire town has been placed under an emergency curfew because of the Sharkodile being spotted in town. (Earlier in the day, he and Clyde had hidden the fake beast in the woods, but they were recorded on camera, and the person who recorded the footage sent it to Katherine Mulligan, who once again believed it to be true.) With the town under emergency curfew, the tree-lighting ceremony at the mall is canceled, which upsets Lincoln even more than the news he had heard the previous day since he was looking forward to seeing Lily light the tree. He tries to call Mulligan and confess that the Sharkodile is a hoax and he was responsible for it, but the news reporter believes him to be a prank caller and ignores him. Lincoln then asks Clyde to help him prove that he is right, so the two of them retrieve the Sharkodile from the woods and drive it to the mall to reveal the truth to Mulligan. However, they get chased down by Rip Hardcore, a celebrity survival expert hired by Mulligan to protect people from the beast. As soon as the boys realize that they are being chased, they take a shortcut to the mall. While taking the shortcut, they pass in front of Lincoln's house, and Lisa, having seen the Sharkodile, begins chasing it down, preparing to tranquilize it and study for science. The other girls, along with Lynn Sr., who has just recovered from the effects of the tranquilizing spray, chase after her, fearing for her safety. Later on, Rita picks up Lori off the highway, ready to take her home safely. Suddenly, the Sharkodile passes by, and Lisa arrives soon after, then commandeers the family van as a means of transport to catch up to the Sharkodile. Eventually, Lincoln and Clyde arrive at the mall, ready to confess the truth about the Sharkodile to Mulligan, but Rip Hardcore does not stop his car; he continues to chase after the beast, which causes the boys to take it into the mall. Before long, they crash the Sharkodile into a bunch of decorations, which gives Lincoln the opportunity to reveal the truth in front of the public. He confesses the entire operation to his family, Rip Hardcore, and Mulligan. Knowing that Lincoln did not have any malicious intentions, they all forgive him, and Mulligan decides to recommence the tree-lighting ceremony. Later on, Lily lights the tree at the mall, setting the mood for everyone to enjoy the holiday after all. The next morning, Lincoln reveals that the other conflicts have been resolved; Luna and Sam are back together, Leni has been rehired at her former workplace, Luan has been re-booked for her comedy gig, and the entire family is now cleared to travel to Miami. However, he also reveals that he has been criminally punished for the property damage he caused by being sentenced to 300 hours of community service. However, before everyone leaves for Miami, Lincoln finds out that his sled has been fixed, and Lisa makes it snow, allowing them all to use the sled as he had planned.