So the movie starts off w John and Sarah sitting in a small beach bar in mexico deciding how to move on after T2. Rando Terminator rolls up and unloads 3 shotgun blasts to little Johns chest and kills him. Sarah is knocked out by the terminator and comes to to find John dead and then it shows title and jumps to modern day. Set in Mexico City the augmented human arrives and finds the new john connor who is the daniella character and they go on the run from the rev 9. Sarah comes and saves them on freeway and tells them she found them via gps texts she gets randomly w coordinates to terminators so she hunts them. The augmented human runs the coordinates on the text and she has the same coordinates tattooed on her body, so they go there and find arnold. He is the same t1000 that killed john in the beginning. He lost his purpose after killing john so he just lived a life and developed a kind of conscience so he decided to help sarah find a purpose by texting her the coordinates. SO they all team up and kill the rev9. Big twist i guess is that skynet never existed but humans created a program called LEGION that basically became the new skynet. Judgment day happens in like 2020 something.