A black cat with striking red stripes leads an intriguing double life. By night, he partners with a cunning cat burglar known as Nico (who affectionately refers to him as Mr. Cat) to pull off daring jewel heists. In contrast, during the day, he enjoys a more peaceful existence with a girl named Zoé (calling him Dino). Zoé, who lost her voice following the tragic death of her father, has grown distant from her mother, Jeanne, a dedicated police superintendent, and relies on the care of their nanny, Claudine.
Nico bestows upon Dino a charming fish-shaped bracelet, which Dino later gifts to Zoé. Meanwhile, at the police station, Jeanne briefs her fellow officers about the security measures surrounding the Colossus of Nairobi statue—an item that cost her husband his life due to the notorious Victor Costa's actions. Victor has sinister plans to target the statue once more during its transport, employing an array of accomplices who go by quirky codenames: M. Bébé (Mr. Baby), M. Hulot, M. Grenouille (Mr. Frog), and M. Patate (Mr. Potato).
Back at home, Jeanne's interest piques when she comes across the fish-shaped bracelet, which she then shows to her colleague Lucas. Lucas connects the bracelet to other stolen items from Rue Mouffetard. That night, Zoé sneaks out to follow Dino and accidentally discovers a hideout for Victor's gang, realizing that Claudine has been providing Victor with insights about police movements. Spotted by the gang, Zoé is saved just in time by Nico, who then takes her to the zoo as a hiding place. But Victor's gang is hot on their trail, forcing Zoé to flee in a boat.
Lucas uncovers evidence linking the robberies to Nico's address. Upon Nico's return to find Zoé there, he is apprehended by Jeanne and Lucas, who believe he has kidnapped her. Jeanne, thinking Zoé is safe with Claudine, leaves with Lucas to chase down Victor. Unbeknownst to them, Nico manages to escape to find Zoé, and Jeanne eventually learns the truth about Zoé's situation through Nico's claims.
Claudine, however, has taken Zoé to Victor's lair, locking her away. With a keen sense, Dino follows Claudine's perfume, guiding Nico to the location. In a brilliant rescue operation, Nico manages to free Zoé by cutting the power and using night goggles. The chase leads them to Notre Dame, where a dramatic confrontation unfolds. Nico attempts to mislead Victor but falls in the process, only to be saved by Jeanne, who arrives just in time.
As Victor corners Zoé, Jeanne, along with Nico and Dino, swoops in for the rescue. In a tense moment, Nico must save Dino from a precarious drop as Jeanne bravely faces off against Victor. Gathering her courage, Jeanne ultimately saves her daughter by striking Victor and sending him into a bewildered trance. In a turn of fate, while attempting to reach what he believes is the Colossus of Nairobi, Victor meets his end in a dramatic fall.
The aftermath sees the rest of Victor's gang, including Claudine, apprehended, while Zoé miraculously regains her ability to speak. Nico undergoes a transformation, leaving behind his life of crime to integrate into the family dynamic, with Dino becoming their beloved pet. As a heartfelt Christmas gesture, Nico presents Jeanne with a snow globe featuring the majestic Cathedral of Notre Dame, symbolizing new beginnings and family bonds.
