When John Connor (Jason Clarke), leader of the human resistance against Skynet, sends Kyle Reese (Jai Courtney) back to 1984 to protect his mother, Sarah (Emilia Clarke), from a Terminator assassin, an unexpected turn of events creates an altered timeline. Instead of a scared waitress, Sarah is a skilled fighter and has a Terminator guardian (Arnold Schwarzenegger) by her side. Faced with unlikely allies and dangerous new enemies, Reese sets out on an unexpected new mission: reset the future