The former secret agent in The Leopard is named Aurelio Zen (played by Jean-Paul Belmondo), who retired to live a quiet life in Formentera after a failed mission that cost him his career and his marriage. Zen is an eccentric, middle-aged man who spends his days writing his first novel about the fictional hero Le Léopard, a suave and fearless French spy.
However, Zen's peaceful life is shattered when his former boss, Colonel Finzi (played by Michel Beaune), asks him to come back to work for one more mission. Finzi believes that an enemy spy known only as "The Hyena" is planning something big, and he wants Zen to use his expertise to uncover the plot. Initially hesitant, Zen eventually agrees to take on the mission, in part because he wants to prove himself to his ex-wife and his former colleagues.
Zen is reluctant to work with anyone, but he is reluctantly helped by a local old maid named Lise (played by Claudia Cardinale). Lise is a tough and resourceful woman who knows the island like the back of her hand, and Zen soon realizes that he can't do the mission without her. As they investigate, they uncover a complex web of deception and betrayal that leads them all the way to Paris.
The Leopard is a stylish and action-packed spy thriller with a sense of humor. It was directed by Jean-Pierre Melville, who was known for his cool, minimalist style. The film's cast also includes Michel Beaune, Adalberto Maria Merli, and Henry Silva. It was released in 1963, and it remains a classic of the genre.