A French chef named Costello travels to Hong Kong after his daughter and her family are brutally attacked. This trip is not just familial; it's driven by a deeper, more personal reason. Years earlier, Costello was once a professional hitman, and his skills still haunt him. Enlisting the help of three local hired guns, Costello embarks on a quest to find those responsible for the attack. Despite facing language barriers and culture shock, he forges an uneasy alliance with the trio, and together they begin to unravel the web of violence and betrayal that led to the attack on his family.

As the investigation progresses, the group navigates through the intricate underworld and faces danger at every turn. Gradually, they identify the individuals behind the crime, subverting obstacles and engaging in complex, high-stakes confrontations. Costello's resolve is constantly tested by his failing memory and the harsh reality of his age, yet he remains determined to exact revenge. With each step closer to the truth, Costello and his comrades are drawn into a deeper conspiracy, forcing them to confront their own demons as they plot their final moves.