 In Montreal, the middle age thief Marcel Talon has spent a great part of his life in prison. When he leaves his confinement on probation, he promises to his beloved girlfriend Maggy that he will find an honest job and have a decent life with her. Indeed Marcel has schemed the greatest heist to a bank ever happened in Canada, and he joins his old friend Fred Giguère and his non-reliable pal Smiley and proposes to dig a long tunnel underground Montreal along the sewers for three months to reach the cellar of the Montral Bank. Fred s grandson and a friend of Smiley join the gang and along the robbery, an unexpected betrayal of his accomplices Smiley and Savard destroy the retirement plan of Marcel.