The Terminator franchise has always been a heady and delicious mixture of horror, sci-fi, and action; time travel, robots, and apocalypse. Every installment in the franchise has spoken of a coming Judgment Day: the apocalyptic moment when machines would rise up and nearly destroy humanity. Afterwards, one man—John Connor—would organize a resistance and fight back, saving the human race. Each film (and TV show) has been about a killer machine coming back through time to try to eliminate John before he can become this savior. Luckily, the resistance has always been able to send back a protector, as well, to keep him safe. We've never really seen the world after Judgment Day, and never really seen John as the savior, except in brief glimpses.
