The directors of a company threatened by a railroad construction project in Africa decide to have the General Secretary of the Franco-African consortium killed. Géo Paquet, known as "Le Gorille", a DST spy, attempts to infiltrate the gang.

Tulipe, is an old man who lives alone in an old railway carriage in the Argentueil region of Paris. His main passions are gardening and oil painting, but he also has a secret source of income. His godson discovers that Tulipe is actually a master forger, producing perfect copies of 10 franc notes. His godson’s girlfriend sees this as an opportunity to get very rich – but she must persuade Tulipe to forge 500 franc notes. Assuming Tulipe’s agreement, his godson and his girlfriend buy an expensive new car and luxury villa in provincial France – but there is a cruel turn of fate in store for them when Tulipe strikes up a friendship with a millionaire playboy.