After the brutal killing of his family, British Special Forces ex-agent John Steel arrives in New York with one purpose: find the person responsible and exact his revenge.

NYPD detective Samantha McCall is investigating a triple homicide when Steel shows up to help find the perpetrator and bring him to justice. What appears to be the work of a serial killer soon turns out to be something different altogether, with relentless mercenaries, a shadowy informant and ghosts from the past for both McCall and Steel all involved.

As unexpected alliances and Steel's personal mission reveal a complex web of treachery, can he and McCall find a way to work together and solve the case?