Robert McCall, a former Marine and Defense Intelligence Agency operative who now lives a relatively quiet life, works as a Lyft driver while secretly serving as a vigilante. Using his extensive skills, McCall seeks to help those who cannot protect themselves, serving justice and retribution against those who exploit the vulnerable. His typical routine sees him reading classic literature, sharing wisdom with his neighbors, and subtly steering the less fortunate onto a better path. However, his tranquil exterior belies the precision and deadliness he wields against the injustices he witnesses in his daily life.

McCall's life takes a personal turn when his close friend and former colleague, Susan Plummer, is brutally murdered while investigating what appeared to be a routine murder-suicide. Driven by loyalty and a sense of duty, McCall commits himself to finding those responsible for Susan's death. His pursuit of vengeance leads him into a conspiracy that runs deeper and is more complex than he anticipated. His mission exposes him to different facets of his past and forces him to confront questions about morality, justice, and how far one can go in the name of retribution. As he peels back the layers of the mystery, McCall finds himself up against a group of highly skilled assassins who will stop at nothing to protect their secrets.