With the commercial failure of the Terminator 3: Rise of the Machines video game, Atari was hard-pressed to create another Terminator game based on the third movie. The sub-title Redemption is said to reflect both the "redemption" of the Terminator's mission half-way through the story and also to reflect a redemption for the Terminator franchise.
The story starts in the year 2032 with a squad of Tech-Com soldiers storming a Skynet facility just in time to stop a T-X from entering the time displacement equipment. However, they are no match for the T-X's superior capabilities and all are gruesomely killed. She manages to enter the TDE without any fuss.
Meanwhile, Kate Connor and the Resistance ambush the T-850 that was responsible for the death of John Connor. Rather than destroy the machine, Tech-Com's technician Daniel is called in to reprogram the cyborg to be sent back to 2003 to protect Kate and John's earlier selves. Shortly after, Daniel is quickly killed by an aerial H/K attacking the base, but the T-850 shoots it down and he is sent by Kate to fight his way to the time displacement machine.
The T-850, with the assistance of several Tech-Com soldiers manages to fight his way to the main gate of the Skynet bunker but is forced to retreat when ambushed by two aerial H/Ks. He destroys them both but his helicopter is shot down by a T-900 (Skynet's standard ground machine soldier it uses, constructed similar to the T-850). He manages to reach the Skynet bunker again by taking control of a ground H/K but a helicopter gets him inside and he "travels back to 2003 to ensure the survival of John Connor and Katherine Brewster".
During the T-850's battle with the T-X in the Cyber Research Systems building, he is thrown into an electro-magnetic accelerator, which is revealed to be a primitive time displacement machine, and is sent back to an alternate 2032 where he discovers that both Kate and John have been terminated and humanity exterminated.
In this bleak reality, freed from the need to constantly fight off the Resistance, Skynet has been able to create a number of massive machines made to rebuild the planet in Skynet's image. In order to reach the TDE, the T-850 must first pilot an FK Venom through the ruined streets to reach a giant FK Titan. Hijacking the Titan, the Terminator then pilots it towards a parked FK Carrier. Boarding the Carrier, the T-850 manages to fight off several attacks before the vehicle is too damaged to fly, where it then crash lands into a terraforming plant. The T-850 then pilots an FK deep into the base, where it then uses a Venom to catch up to and commandeer an escaping FK Bomber, which it then flies into the Time Displacement Chamber. Defeating chamber's guardians and reactivating the device, the T-850 travels back to the present.
However, not all is lost as the Terminator once again fights his way through Skynet and sends himself back to 2003. He appears just in time to fight off the T-X with John and Kate trying to escape to Crystal Peak. By this time, the T-850 fights with not only the T-X, but other T-800's that were reprogrammed.
In the final moments, the T-850 is shot down by the T-X and his fuel cells are ruptured, slowing him down. However, he prevents the T-X from reaching John and Kate by blocking her route to them, and eventually catches up to them and places his Hydrogen fuel cell in her mouth, thus leading to the destruction of both Terminators.
However, John is later revealed to have found the Terminator's barely functioning Endoskeleton skull and he removes its processing chip, thus deactivating it. The cutscene opens again to another cyborg's point of view and a much older John is seen giving orders to soldiers.
He introduces himself and it is made clear to the player that they are now in the future and the T-850 has been "resurrected" into an extensively modified FK Reaper. John orders the Terminator to provide cover fire and it stomps into battle, aiding the Human Resistance once again. The game concludes with the words: "The battle has just begun...".
- The game parallels most of the main events of Terminator 3: Rise of the Machine film (albeit with a few modified scenes to reflect a faster pacing and more serious tone of the game), until reaching a plot twist at the middle. During the T-850's battle with the T-X in the Cyber Research Systems building, instead of losing the fight and being reprogrammed by the T-X, he is thrown into an electro-magnetic accelerator, which is revealed to be a primitive time displacement machine, and is sent back to an alternate future 2032.
- The cutscene after the T-850 destroyed the T-X along with itself parallels the movie ending.
- According to video clips from IGN, the Heads Up Display for the Terminators in The Sarah Connor Chronicles will be based on the Terminator HUD from this game.