Dandelions by the Roots (1964)

Original title: Des pissenlits par la racine

Jockey Jack has a bill open with a gangster just released from jail. He somehow manages to parry the gangster's knife attack backstage at a theatre and the latter ends up dead being put into a double bass case. A day later the gangster mysteriously has disappeared, but it turns out that he was carrying a bet ticket for a horse race now worth over a million. A turbulent run for the money begins.