Denzel Washington is Robert McCall. McCall has both a mysterious past, and a set of special skills. He is 'retired' from his former life with no intention of returning to it. But then he meets Teri, a young girl who has fallen under the control of the Russian mob. McCall can't stand idly by, and decides to help her.
The story is very well-told and engaging, with an appropriate level of tension throughout. Denzel is particularly good as McCall. IMHO, the ending implies there might be a sequel, and I sure hope there is :)
Content warnings include violence, and language.