In a prologue, we see that the Mother is a pregnant FBI informant. She warns the agents in her safe house, including William Cruise (Omari Hardwick), that something bad’s about to go down. After it does, she’s forced to sign over her newborn daughter (whom she nearly lost in a knife attack) to protective custody and relocate to remote Alaska. 12 years later, a criminal syndicate has IDed the girl, named Zoe by her adoptive parents (Lucy Paez), and wants revenge. Lopez’s character gets back into action with Cruise as her sidekick to save the life of the child she only knows from pictures.
In flashbacks, we learn the Mother met the film’s two antagonists — Adrian Lovell (Joseph Fiennes) and Hector Álvarez (Gael García Bernal) — while she was stationed in Afghanistan and at Guantanamo Bay. Lovell, her sniper trainer, recruited her into arms dealing and she caught Álvarez skimming guns. She used romantic relationships with both men to set up mutually beneficial business interests. But when she discovered that Lovell and Álvarez were smuggling children, too, she could no longer remain complicit in their crimes.
In the present timeline, Álvarez’s henchman kidnap Zoe and take her to his compound in Cuba. The Mother and Cruise are able to free her and kill Álvarez. Lovell, having survived the explosion 12 years earlier, stages a kidnapping attempt of his own shortly thereafter. He crashes his SUV into Cruise and Zoe’s SUV, and the Mother, on motorcycle, barely escapes with Zoe to her hideout in Alaska.