Miles Dyson worked for Cyberdyne Systems Corporation as head of development for a new type of neural-net based proccessing system, an artificial intelligence capable of operating automated defense systems without the need for human intervention. Although his work is based on components salvaged from a destroyed Terminator, he is unaware of the origin or nature of the technology he is studying.
When Sarah Connor is made aware of Dyson's involvement in the coming Judgment Day, she decides to take off on her own to kill Dyson before he can complete SkyNet. She arrives at the Dysons' residence and tries to kill Miles with a CAR-15 rifle, but Dyson ducks down as she shoots, alerting him and his family. Sarah then bursts into the house to finish Dyson and holds him at gunpoint, but after seeing Miles' family and his expression of terror and confusion, Sarah finds herself unable to commit the deed as clearly Dyson is not the heartless monster she had imagined him to be.
After Sarah's son John and his Terminator guardian arrive, the Terminator shows Dyson what the future holds by cutting the flesh off its arm, revealing the skeletal metallic arm beneath. The Terminator explains how Dyson's project will result in a nuclear holocaust and a war between humanity and machines. After listening to this explanation and witnessing the living evidence of the nightmarish future, Dyson agrees to help the Connors stop SkyNet's creation. The group visit CyberDyne Headquarters where they demolish the laboratory and steal the CPU chip and arm from the Terminator that was destroyed back in 1984.
When the police arrive to investigate the attack on CyberDyne, Dyson is struck by gunfire. His wounds are fatal and he urges the Connors to flee while he sets off the bomb in the lab. He sits beside the bomb, holding a broken piece of a model of the Terminator CPU above the triggering mechanism. His breathing is erratic and it is clear he won't last long. When the SWAT team find him sitting by the bomb, gasping what will be his last breaths, Dyson urges them to get out before he gasps his final breath and drops his arm on the bomb trigger. The SWAT team make it out just in time as Dyson loses consciousness and his arm hits the bomb trigger, blowing up the lab and a sizeable chunk of CyberDyne HQ.