Martin (Michael J. Fox) just returned to the real world to reunite with his girlfriend, and Dr. Brown (Christopher Lloyd) anxiously took them to the future world 30 years later. It turned out that this time, Martin's two children in the future were imprisoned for participating in robbery, and the doctor wanted to take Martin with him to prevent the tragedy from happening. After some maneuvers, the two children were successfully rescued, but when the three returned to the real world, they found that the surroundings had changed drastically. The world was controlled by Bev (Thomas F. Wilson), Martin's father George died tragically, and his mother Lorraine (Lea Thompson) became Bev's wife! All this was because the secret of the time machine was accidentally discovered by the old Bev in the future. He secretly went back to make trouble, and as a result, the whole world was under his control! Martin and the doctor embarked on the journey of time travel again, hoping to get the world back on track.