McCall receives a desperate plea for help from her former CIA trainee, now a full-fledged agent, that leads her into a confrontation with Mason Quinn, the most dangerous enemy from her past in intelligence. In need of confidential information about the agent's latest assignment, McCall forms a tentative alliance with Carter Griffin, a by-the-book CIA handler.
Robyn McCall, an enigmatic woman with a mysterious background, uses her extensive skills to help those with nowhere else to turn. McCall comes across to most as an average single mom who is quietly raising her teenage daughter. But to a trusted few, she is "The Equalizer" - an anonymous guardian angel and defender of the downtrodden, who's also dogged in her pursuit of personal redemption.