Rio de Janeiro, during the city’s vibrant Carnival, becomes the backdrop for a plan that relies on brains, timing, and nerve. Professor James Anders, Edward G. Robinson, a seemingly mild-mannered American teacher working abroad, grows tired of the classroom and decides to retire from teaching with a mission of a different sort. Rather than settle into quiet days, he sets out to assemble a crack team to pull off a diamond heist that would take place right at the heart of the celebrations.
With the help of Mark Milford, Adolfo Celi, an old friend who has turned to crime, Anders recruits four international experts to execute the robbery: Gregg Hutchinson, George Rigaud, a meticulous English safecracker; Agostino Rossi, Riccardo Cucciolla, an Italian mechanical and electronics genius; Jean-Paul Audry, Robert Hoffmann, a French playboy charged with seducing the only woman with a key to the vault, the lovely Mary Ann, Janet Leigh; and Erich Weiss, Klaus Kinski, a German ex-military man. The ensemble is designed to breach a building that guards the diamonds with layers of protection, from precision sensors to a cutting-edge safe system.
The crew crafts a plan built around a pair of daunting obstacles: the entry corridor’s photocell beams and the upcoming “Grand Slam 70” safe system, a sensitive setup designed to trigger an alarm the moment any sound or disturbance is detected near the vault. The group’s confidence is tested when they encounter the latter system, but Agostino’s ingenuity helps them devise a workaround that keeps the operation on track, even as the clock ticks toward the carnival’s climax.
Step by step, the team executes the infiltration. A pneumatic trestle lets them crawl over the photocell beams, and Jean-Paul uses Mary Ann’s key—taken during a tense exchange—to gain access to the building’s inner sanctum. The safe is shifted into the corridor using shaving cream to dampen sound, then opened with carefully placed nitroglycerin charges. The plan succeeds in principle, and the diamonds appear within reach as the crew makes their escape.
But triumph quickly falters. The day after the robbery, Mary Ann discovers that the key had been temporarily taken, alerting the authorities and triggering a frantic pursuit. As the team navigates a roadblock, Jean-Paul is identified, and Gregg dies in the ensuing chase. In a brutal twist, Erich betrays his partners and murders Jean-Paul, while Agostino escapes back to Rio to be with Setuaka, [Jussara], only to fall victim to police bullets.
Back at the meet point, Erich delivers the diamond case, but Milford intercepts and discovers the case is empty. Anders, meanwhile, reunites with Mary Ann in a Rome cafe, their partnership sealed in crime as they swap the fake for the real gems. Yet their luck doesn’t hold, and the diamonds slip away once more when two thieves on a motorcycle snatch them from the couple.
In the end, the plan exposes the perilous charm of such schemes: a craftily engineered heist that dazzles with its technical detail and global cast, yet is undone by paranoia, betrayal, and the slippery line between loyalty and greed. The carnival’s glow fading into night, the characters are left with the lingering question of what cosmic balance keeps the prize just out of reach.
