In the year 2034 the world is in ruins, it is dominated by machines and humans serve as their slaves. A few hundred humans fight against their opressors. This group of humans is called The Resistance, led by John O’Connor.
To ensure their domination a couple of robots were sent to the past with the mission to kill John. John got his hands on one such robot and with the help of The Resistance this robot was reprogrammed with the sole purpose of protecting Johns younger self. This robot was sent to the past as well.