The film starts with a familiar premise: Agents J and K are on a mission to protect Earth from various alien threats. However, their latest adversary, Boris the Butler (Thandie Newton), escapes with a powerful device known as the "Neuralyzer's arch-nemesis," which can erase people from existence. The agents soon discover that Boris plans to travel back in time to 1969 to kill the young scientist who created the neuralyzer, thereby preventing its invention and altering the course of history.