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.

McCall and Dante's relationship is tested when a conman the NYPD has been building a years-long case against kidnaps a relative of McCall's client and forces him to assist in a heist in order to save them.

When a former Chinese MSS agent is poisoned and comes to McCall for help, McCall tracks down the perpetrators and the antidote. Meanwhile, Aunt Vi encourages Dee to protest against a well-known climate change denier.