The Cyberdyne Systems Model 101 Series 800 Version 2.4 Infiltration-Combat Unit was sent from the future to arrive in Acton,California on June 8, 1995. Its misson was to protect young John Connor, which it successfully completed.
To protect his younger self in the past, John Connor reprogramed this Terminator and sent it back in time via the time displacment sphere. Upon arrival, it encountered a group of bikers, stealing one's clothing and the bar owner's sunglasses and shotgun.
The T-800 then tracked down John Connor in a shopping mall. When it met the T-1000 sent by Skynet to kill Connor, a lengthy chase ensued, but the two managed to escape the T-1000. Connor questioned the Terminator about itself and who sent it. The Terminator answered that it is a cybernetic organism, having living tissue over its metal endoskeleton. It told John that it was his future self who sent it to protect him.
John and the Terminator go to the Pescerado State hospital to help free John's mother, Sarah. The three manage to go to the garage, and Sarah almost succeeds in killing the Terminator by smashing its CPU chip, but was stopped by John, who felt that it was needed. He learns that the Terminator has the capacity to learn. When Sarah asks it who built Skynet, it answered that it was Miles Dyson. It explained that Skynet became self-aware after its creation and began to deny human authority.
The group later encountered Dyson, but didn't kill him. The Terminator explained to Dyson the consequences of his research. The three, along with Dyson, attempted to destroy the Cyberdyne building to prevent Skynet from being created. They were soon approached by the police. John, Sarah, and the Terminator escaped the building while Dyson blew up the building with himself inside.
The three were encountered again by the T-1000. The Terminator succeeded in destroying it when it falls into molten steel. John drops the CPU and the arm of the first Terminator into the hot liquid. Since the Terminator had a computer chip in it, it also planned to destroy itself to prevent its technology from being discovered by others to create Skynet. John begged it not to be destroyed, but it had to fulfill its mission. When John cried, the Terminator understood why, but could not cry itself because it was a machine. It hugged John for the first and very last time, and having finally earned Sarah's respect, shook her hand offered to a brother warrior. As it is lowered into the steel below, the Warrior of Steel-in-Flesh gave John an encouraging thumbs up before sacrificing its life for humanity's future.