Hugo is an orphan boy living in the walls of a train station in 1930s Paris. He learned to fix clocks and other gadgets from his father and uncle, which he puts to use keeping the train station clocks running. The only thing that he has left that connects him to his dead father is a mechanical man that doesn't work. Hugo needs to unlock the secret he believes it contains. On his adventures, he meets a shopkeeper who works in the train station and his adventure-seeking goddaughter Isabelle. Hugo and Isabelle try to unlock the old man's memories.
