On October 26, 1985, Dr. Emmett Brown arrives in the DeLorean time machine and persuades Marty McFly and his girlfriend, , to travel to the future with him and help their future children, with Biff Tannen witnessing their departure. They arrive on October 21, 2015, where Doc electronically incapacitates Jennifer and leaves her asleep in an alley, explaining that she should not have too much knowledge of future events. He has Marty pose as his own son and lookalike Marty Jr. to refuse an offer to participate in a robbery with Biff's grandson Griff, thus saving Marty Jr. from prison.