Decades after Sarah Connor prevented Judgment Day, a new, highly advanced Terminator called the Rev-9 is sent from the future by an artificial intelligence named Legion, which has risen in Skynet's place. Its mission is to eliminate Dani Ramos, a young woman whose fate is critical to the human resistance. As the Rev-9 relentlessly pursues Dani in Mexico City, she is protected by Grace, an augmented super-soldier from the future, specifically sent to keep Dani alive. Caught in a seemingly unwinnable battle, their only hope arises when Sarah Connor, now a seasoned warrior dedicated to hunting Terminators, intervenes just in time to help them escape.

Sarah, Dani, and Grace embark on a desperate quest to evade the unstoppable Rev-9. Along their journey, they seek out the origin of mysterious coordinates sent to Sarah, leading to an unexpected ally—an aging T-800 model Terminator. This T-800 has developed a form of conscience and lives in seclusion, having completed its mission from years prior. Resistant to trust the machine that resembles the one who once wrought havoc in her life, Sarah grapples with old traumas as they form an uneasy alliance. Together, this group represents humanity's last stand against the seemingly inevitable rise of the machines, and they brace for a confrontation that could alter the course of the future.