We first meet our unusual protagonist through the eyes of its co-star, Naoufel, a shy, emotionally repressed pizza delivery boy-turned-carpenter's apprentice. Because of a workplace accident involving a fly and a bandsaw, the hand and its host have become violently separated. Not one to accept its fate among the rest of the removed body parts inside a coroner's office fridge, the hand breaks out in a sequence that pays homage to Luis Bunuel and Salvador Dali's surreal classic Un Chien Andalou, in the form of an eyeball that gets squashed under a gentleman's foot.
The hand wants to return to Naoufel's right wrist, but it won't be easy. It will have to navigate the streets, tunnels, and rooftops of Paris, handling the obstacles with resilience, quick thinking, and luck. During its perilous journey, the hand recalls Naoufel's life before the accident -- mainly his attempt to win over Gabrielle, a librarian who enjoys the work of John Irving and having lots of onions on her pizza -- and his early childhood in Morocco. The latter scenes, animated in black-and-white, show us a much different Naoufel than the one who spends his days delivering pizzas. He was a boy with dreams of becoming both a pianist and an astronaut, who enjoyed using his tape recorder to document the sounds of nature as well as the voices of his loving, artistic parents. His life was filled with music, love, and curiosity. All of that taken away after an accident that would make him an orphan, forcing him to move to Paris to live with his cold, uncaring uncle, and his crass and rude cousin Raouf.
After seemingly years of only the cassette tapes he recorded of his parents to keep him company, Naoufel is aimless. He believes that there is nothing for him in this life -- until he meets Gabrielle through an intercom one evening as Naoufel, already 40 minutes late to deliver her pizza, waits out a downpour after a few failed attempts at opening her lobby door. It's clear from their opening exchange that Gabrielle is both extremely straightforward and the first person in a long time to really talk to Naoufel as a person, not as an employee to belittle, a roommate to emasculate, or as a charity case to ignore.