NYPD Detective Jimmy "Popeye" Doyle heads to Marseille, France, following the trail of the elusive drug-smuggling mastermind Alain Charnier, whom Doyle had narrowly missed capturing in New York. Unfamiliar with the local language and customs, Doyle struggles to assert his methods and authority with the French police, who are wary of his brash and unorthodox techniques. Tasked with working alongside the more methodical and reserved French detective Henri Barthélémy, Doyle finds himself in a clash of cultures and police work philosophies. Despite their differences, they are united by a common goal: to track down Charnier and dismantle his expansive heroin network.

As Doyle delves deeper into the underbelly of Marseille's narcotics trade, he becomes increasingly isolated and vulnerable in a city where he has no jurisdiction or backup. His relentless pursuit of Charnier leads him into dangerous situations, putting not only the investigation at risk but also his own life. The detective's determination to catch Charnier becomes a personal obsession, pushing Doyle to the limits of his endurance and beyond. Meanwhile, Charnier, always one step ahead, seeks to exploit Doyle's weaknesses and continue his lucrative operation, setting the stage for a high-stakes game of cat and mouse that tests the resolve of both men.