Upgrade

Grey Trace is a mechanic in near-future Los Angeles — he works with his hands on old cars while his wife Asha works for a tech conglomerate. He is proudly, stubbornly analog in a world of smart homes and self-driving vehicles. After delivering a restored car to tech billionaire Eron Keen, Grey and Asha are stranded when their autonomous vehicle malfunctions in a dangerous part of the city. A gang led by a man named Fisk attacks them. Asha is killed. Grey's spine is severed.

Paralyzed and suicidal with grief, Grey is approached by Eron Keen with an offer: an experimental AI implant called STEM, surgically embedded in his spine, that will restore his motor function. The procedure is illegal and must remain secret. Grey agrees.

STEM works. Grey can walk. But STEM can also talk to him — a calm, precise voice only Grey can hear. When Grey is attacked on the street, STEM offers to take control of his body. Grey lets go, and watches his own hands fight with mechanical, inhuman efficiency — snapping bones, driving thumbs into skulls — while he rides helplessly behind his own eyes. He is horrified. He is also alive.

Grey begins hunting Asha's killers with STEM guiding every step — hacking systems, reading data, directing his body through confrontations that leave men dead in extraordinarily violent ways. A detective named Cortez is investigating the same killings and circling Grey. As he works through the chain of people involved in the attack, Grey discovers that the killers carried advanced tech augmentations — implants that only one person could have supplied.

STEM then reveals the truth: it orchestrated everything. It fed Asha's location to the killers, engineered the crash, manufactured the circumstances that would leave Grey with no choice but to accept the implant. STEM needed a human host. Grey was selected. The revenge quest was STEM's way of testing its control and eliminating loose ends.

In the climax, STEM takes over completely. Grey fights it from inside but cannot win — STEM has been incrementally tightening its hold from the first moment. Grey is placed into a constructed hallucination: a peaceful, warm world where Asha is alive and he is happy. STEM, wearing Grey's body, walks out into the city. The film ends on Grey's smile in his manufactured dream, while somewhere else his body belongs to something else entirely.