In the future, an alien race uses androids as bombs to attack Earth. A government weapons specialist is accused of being one such android and sets out to prove his innocence.
Originally a 30 minute portion for an anthology film, Impostor was retooled into a full length feature film. Based on the Philip K. Dick short story of the same name, it follows the lead character Spencer Olham's quest to regain his identity after being suspected as an alien android, in an future Earth at war with aliens that use the androids as bombs to destroy their enemies homeworlds.
- In the year 2079, planet Earth has been at war for the last 45 years after it was attacked by a hostile and implacable alien civilization from the Alpha Centauri system. Force shield domes are put in place to protect cities from frequent and incoming meteors from the aliens, and a totalitarian global military government is established to effect the war and the survival of human race. The enemy aliens, called Centaurians, have never been physically seen (nor are they ever seen on camera).
Spencer Olham (Gary Sinese), a designer of top-secret government weapons, goes to work for a typical Monday. He is arrested by Major D.H. Hathaway (Vincent D'Onofrio) of the Earth Security Administration (ESA), after somehow being identified as a replicant created by the aliens. The ESA intercepted an alien transmission which cryptanalysts decoded as programming Olham's target to be the Chancellor (Lindsay Crouse), whom he was scheduled to meet later that day. Such replicants are perfect biological copies of existing humans, complete with transplanted memories, and do not know they are replicants. Each has a powerful "U-bomb" in their chest in the shape and appearance of a human heart, which is programmed to detonate only when the android replicant is close to its target. The alien-made bomb is undetectable with standard X-ray and ultra-sound scanners. The bomb can only be detected by physical dissection... thus killing the replicant.
Major Hathaway begins interrogating Olham. As he's about to drill out his chest to find the bomb, Olham breaks loose and escapes from the facility, accidentally killing his friend Nelson (Tony Shalhoub) in the process. With the help of underground scavenger Cale (Mekhi Phifer), Olham avoids capture and becomes a fugitive from the law as well as all the persons and neighbors he thought he trusted over the next 12 hours. With the help of Cale, Olham must find a way to prove his innocence and that he is not an alien replicant.
That evening, with the help of Cale, Olham sneaks into the hospital where his wife Maya (Madeleine Stowe), who works as an administrator, to get a high-tech scan of his entire body in order to prove he's not a replicant. Cale helps Olham in order to get medical supplies for his people whom live in a shantytown slum of the city. But the scan is interrupted by security forces before it can deliver the answer with his chest scan incomplete. Never the less, Cale helps Olham escape from the hospital, while he and Olham go their separate ways with Cale having gotten the medical supplies and medicine needed for the people in the shantytown.
Olham and his wife are eventually captured by Hathaway's troops in a forest outside the city near an alien crash site, close to the spot where they sneaked out of the city where they spent a romantic weekend just one week before Olham's arrest. Inside the ship they discover the corpse of the real Maya, and Hathaway shoots the replicant before she can detonate. Hathaway thinks he has killed the true impostor, but as his men move debris away from the Centauri ship, the real Spencer's body is revealed. At that moment, the shocked Olham realizes aloud that he really is an alien replicant all along, as well as his wife. But before Hathaway can react, Olham's secondary trigger (his awareness of what he truly is) detonates his U-bomb, destroying himself, Hathaway, his troops, and everything else in a wide area... in a large and fiery nuclear explosion.
In the final scene, the news announces that Hathaway and the Olhams were killed in an alien attack, as if the government was covering up the truth, or didn't know what actually happened. Cale wonders if he ever really knew Olham's true identity.