The story begins with Hugo Cabret, an orphan living in a train station, attempting to steal a windup toy from a toy shop owned by an old man named Georges. Georges catches Hugo and takes Hugo’s notebook from him. This incident is upsetting to Hugo; the notebook contains his deceased father’s drawings of an automaton Hugo is trying to put back together. After Hugo loses the notebook, he makes friends with Georges’ adopted daughter, Isabelle. Together, Isabelle and Hugo scheme up a way to get Hugo’s notebook back. Hugo is happy for Isabelle’s help, but he repeatedly warns her not to look in the notebook if she finds it.
While Isabelle is looking for the notebook, Hugo gets a job with Georges. Georges tells Hugo that he might give him his notebook back if he works for free to make up for what he stole. Hugo agrees to the job, which he largely enjoys, although he continues stealing when he thinks Georges isn’t looking. While working for Georges, Hugo notices that Georges knows a lot of magic tricks. Hugo is interested in magic because magicians were often responsible for creating the early automatons, which they used as part of their act. Hugo wonders why someone like Georges—who is grumpy and antisocial—would know so much about magic. One day, Hugo meets Isabelle in a bookstore where she introduces him to her friend, Etienne, an older boy who works at a movie theater. Isabelle tells Hugo that Georges won’t let her go to the movies, so Etienne sneaks her in for free. The following week, Isabelle and Hugo go together to Etienne’s theater, only to find out he has been fired. Luckily, Isabelle knows how to pick locks and she gets them into the theater all by herself. Isabelle and Hugo have a great time, although the theater’s manager throws them out once he realizes they’ve snuck in.
One day, when Hugo goes into work, Georges starts yelling at him. He thinks Hugo broke into his house and stole his notebook. Hugo doesn’t know what he is talking about until he spots Isabelle outside the shop with the notebook in her hand. Hugo runs up to Isabelle and takes the notebook, along with a key Isabelle wears on a necklace around her neck. Then, Hugo returns to his secret apartment in the train station where he keeps the automaton. At this point, the automaton is almost fully functional. The automaton has a pen in its hand, and Hugo knows that it will write something when he turns it on. However, to turn it on, he needs a key. Luckily, the key he took from Isabelle fits, just as he thought it would.
Just before Hugo can turn on the automaton, Isabelle breaks into his room and demands to know what is going on. Hugo refuses to answer, but eventually she spots the automaton and turns it on herself. Although it takes some time, the automaton eventually draws an elaborate picture of what looks like a moon with a face, which has a rocket stuck in one eye. Hugo recognizes the image as something his father described to him when he was young. Apparently, it comes from an old movie that was Hugo’s father’s favorite. Once the automaton draws the image, it signs the name “Georges Méliès” beneath it. Isabelle tells Hugo that Georges Méliès is Georges’ full name.
Hugo and Isabelle start investigating to try to uncover the mystery of the automaton. Isabelle’s godmother, Jeanne, who is also Georges’ wife, tells them to leave the matter alone. However, they continue searching anyway. Eventually, they find a lot of elaborately drawn images tucked away in Georges’ bedroom, which all bear his signature. Unfortunately, Georges happens to see what they have found, and it causes him to have a breakdown. He becomes ill and unable to work at the toy store, which is especially problematic because he is the only person in the family with an income. Hugo and Isabelle continue to investigate the mystery and run Georges’ shop by themselves in the meantime. After chasing down several leads, Hugo eventually makes his way to the French Film Academy’s library where he finds Etienne. Etienne managed to get a job at the academy, where he is also training to become a filmmaker. With Etienne’s help, Hugo discovers that Georges was once a famous magician and filmmaker. However, for a long time, the French public thought he was dead.
Hugo tells Etienne that Georges is still alive, which prompts Etienne and his professor, Monsieur Tabard, to pay Georges a visit. They bring a projector and one of Georges’ films, A Trip to the Moon, along with them and screen it for Jeanne, Isabelle, and Hugo. Unbeknownst to everyone, Georges watches the film from the hallway and afterwards asks for the projector. Then, he locks himself in his room. Isabelle picks the room’s lock, and everyone looks in on Georges to see what he is doing. As it turns out, Georges has all of his images spread around the room and is watching his film again on the projector. When he sees he has an audience, Georges explains that he was once a great filmmaker until he fell on hard times and had to sell all of his films. This difficult part of his life was made even worse when two of his best friends—Isabelle’s parents—died in a car crash. Ever since, Georges has worked at the toy shop and fallen into obscurity.
To Georges’ knowledge, his only surviving creation, other than what is currently in his room, is the automaton Hugo fixed. He asks Hugo to bring the automaton to him, and Hugo happily agrees to do so. However, while Hugo is at the train station, he gets caught stealing from a café. The owner of the café, as well as the Station Inspector, chase Hugo down and eventually catch him. Then, the Station Inspector throws Hugo in a cage in his office. Not long afterward, Isabelle and Georges show up and explain Hugo’s situation. Georges promises to take Hugo with them and provide him with a home from now on.
Six months later, the French Film Academy holds a celebration in Georges’ honor. With the help of Georges, Hugo, and Isabelle, they managed to find over 80 of Georges’ films, some of which they show at the event. After the event, a small party is held at a restaurant. During the party, Hugo performs magic tricks for a small crowd, and Georges gives him the stage name “Professor Alcofrisbas.” In the final chapter, the story switches to the first person, which Hugo narrates. Hugo reveals that he is an adult now and he works as a magician. Even more impressive, he managed to build an automaton on his own. The automaton is incredibly complex because it can write Hugo’s life story. In fact, according to Hugo, the automaton wrote the entire story of The Invention of Hugo Cabret, illustrations and all.