McCall is a widowed former Black Ops and government soldier who is threatened by Russian mobsters in his hometown of Boston, Massachusetts. He ends up employing his skills and becoming a secretive vigilante after seeing an underage streetwalker be violently abused by the mobsters. He ends up having to also save co-workers he knows at a home depot-type warehouse job when the mobsters seize control of it and hold the workers hostage.
McCall is much like the Mission: Impossible series of films and new television version of "Hawaii Five-0" where despite taking the near-exact premise and retaining some of the same character names and traits, the execution is clearly different and it's own artistic license.
The original Robert McCall on the original television incarnation of "The Equalizer" was portrayed by the late English actor Edward Woodward. The series had writers and show runners who had also worked on series such as "Miami Vice" and later "24". Coincidentally, McCall appears to share some traits with "24"'s lead protagonist Jack Bauer (played by Kiefer Sutherland) as well as movie incarnation of Jason Bourne (played by Matt Damon) in the Bourne Identity series, Bryan Mills (played by Liam Neeson) in the Taken trilogy and title character in John Wick (played by Keanu Reeves) in addition to having a similar filming style.