The Killer follows a cold-blooded assassin who meticulously plans each of his missions, operating under the creed of no emotion, no hesitation, and no remorse. However, after a botched job, he finds himself hunted by the people who hired him and forced to fight for survival. As he goes on the run, he begins to question his own principles and the emotional detachment that once defined him. Through his journey, the line between predator and prey becomes increasingly blurred.