Before story events
In 1930s Paris, young Hugo Cabret and his father repair an automaton at the museum where his father works. When Hugo's father dies in a fire, his uncle brings him to live and work at the train station maintaining the clocks. His uncle disappears, and Hugo keeps the clocks running by himself, living inside the station walls and stealing food from the shops. One day, he rescues the automaton from the burnt museum in hopes of restoring it. Later, he discovers a keyhole in the shape of a heart, and works on finding the key.
Part 1
A few months later, Hugo is caught stealing from a toy booth and is forced to return his stolen tools and mechanisms, as well as his notebook containing his father's drawings of the automaton. Hugo follows the shopkeeper to his house but fails to retrieve his notebook. A girl in the house named Isabelle promises him she will make sure the notebook is not destroyed.
The next day, Hugo returns to the toy booth, where the shopkeeper tells him the notebook has been burnt; he encounters Isabelle, who assures him it is safe. Isabelle brings him to a bookshop to meet her friend Etienne, who sneaks them into the cinema; Papa Georges, the shopkeeper, has forbidden Isabelle from watching films.
Papa Georges forces Hugo to work at the toy booth, with the possibility of returning the Diary; the job further delays Hugo's clock duties. Hugo and Isabelle visit the theater but learn Etienne has been fired for sneaking children in, so Isabelle unlocks the door with a bobby pin. They are kicked out, and Hugo is almost caught by the station inspector. Isabelle asks Hugo about his life, but he runs away, fearing that sharing the truth will send him to an orphanage or prison. Isabelle chases him but trips, revealing a dog-shaped key around her neck, which Hugo realizes is the key to the auto-machine.
The next morning, Hugo learns that Isabelle has read his diary. He pickpockets the key with a technique learned from a book on magic and returns to his hidden room, where he is confronted by Isabelle. They use the key to activate the auto-machine, which produces a drawing of a rocket which has landed in one of the eyes of the "man in the Moon."
Part 2
The automaton signs its drawing “Georges Méliès”, who Isabelle reveals is Papa Georges. Believing Hugo has stolen the automaton, she runs home; Hugo follows, and inadvertently crushes his hand in the front door, and she brings him inside. Hugo notices a strangely locked drawer; Isabelle picks it open but drops the heavy box inside, breaking it and sprains her foot. Georges enters and is enraged, ripping up the drawings inside the box. After Mama Jeanne forces everyone to bed, Hugo takes the key to the toy booth back to the station.
The next day, he and Isabelle collect the money from the booth and buy medicine for Georges. Hugo visits the film academy library where Etienne now works. Hugo finds a book titled The Invention of Dreams with a drawing of the automaton, which he learns is a scene from the first movie his father ever saw, A Trip to the Moon, directed by Georges Méliès. Hugo invites Etienne and the book's author, René Tabard, to Isabelle's house later, and explains Méliès’ career to Isabelle.
At the house, Tabard and Etienne screen A Trip to the Moon, and George finally reveals his past: he was the prolific and innovative filmmaker Méliès, but after World War I, the deaths of Isabelle's parents, and the loss of most of his films in a fire, he sank into depression and burned the rest, to begin a new life at the toy booth. He also created the automaton; excited to learn it has survived, he asks Hugo to bring it to him. Hugo returns to the station, stealing breakfast from Monsieur Frick and Miss Emily as usual; overhearing that his uncle was found dead, Hugo drops the milk bottle and is discovered. He escapes and fetches the automaton, but is pursued by the station inspector. In the chase, Hugo is almost struck by a train but is pulled back by the inspector, and faints.
Hugo awakens in a cell. He reveals everything to the inspector and is released to be adopted by Georges, Mama Jean, and Isabelle. He and Méliès repair the automaton together.
Epilogue: 6 months later
Six months later, Hugo and his new family attend a grand concert including Méliès’ surviving film scenes. Onstage, Tabard acknowledges Hugo, Isabelle, and Etienne for their help in honoring Georges. In the end, it is revealed that Hugo Cabret made his own automaton that wrote and drew the entire book of The Invention of Hugo Cabret.
