Martin (Michael J. Fox) has just returned to the real world to reunite with his girlfriend, when Dr. Brown (Christopher Lloyd) anxiously takes them to the future world 30 years later. It turns out that this time Martin's two future children are in prison for participating in the robbery. The doctor wants to bring Martin to prevent the tragedy from happening. After a while, the two children were successfully saved, but when the three returned to the real world, they found that the surroundings had undergone earth-shaking changes, and the world had been destroyed by Thomas F. Under the control of Wilson, Martin's father George died tragically, and his mother Loren (Lea Thompson) became Beef's wife! All of this was because the secret of the time machine was accidentally seen through by the future Old Beef. He secretly went back to do something, and as a result, the entire world was under his control! Martin and Dr. Dr. once again embarked on a journey of time, hoping to get the world back on track.