''Impostor'' is a 2001 science-fiction film, starring Creator/GarySinise, Creator/VincentDOnofrio, Madeleine Stowe, and Mekhi Phifer. The film was based on a 1953 short story by Creator/PhilipKDick, and [[StillbornFranchise was intended to be the first of a science-fiction anthology]] with the Isaac Asimov story ''The Last Question'' and the DonaldWolleim story ''Mimic'' to follow after.

In the middle of the 21st century, humanity was attacked by an alien civilization from the Alpha Centauri system. The Centauri have bombed Earth continually for over 45 years, reducing large parts of the Earth to wasteland and destroying effective goverment in others. A global totalitarian government takes control and the major cities are fitted with defensive shields to protect the last vestiges of civilization. The Centauri resort to more covert means to destroy humanity, using biorobots armed with atomic bombs to infiltrate the cities and kill key political figures.

Dr. Spencer Olham (Gary Sinise) is a renowned scientist working on government weapons projects. One day he is unexpectedly arrested and accused by Major Hathaway (Vincent D'Onofrio) of the Earth Security Administration of being a robot sent to assassinate the Chancellor during an upcoming meeting. Olham goes on the run and heads to the outer regions to prove his innocence.

!!This film provides examples of:

* AccidentalPublicConfession: Type 3. Hathaway uses film of Spencerís BrandishmentBluff to convince Maya that her husband actually is an imposter.
* AliensAreBastards: The Alpha Centauri aliens attacked humanity and try to destroy Earth civilization for no apparent reason, as their motives aren't revealed in the film.
* ArtificialHuman: The Centauri can create manufactured humans with an atom bomb built into them which will explode if they're exposed to an appropriate trigger.
* BittersweetEnding: [[spoiler:The hero and his wife are dead and one of their roboclones explodes. Hundreds of acres of forest are destroyed, killing thousands of people and Major Hathaway, who had been trying to prevent exactly that from happening the entire film. The assassination of the Chancellor has been prevented however and Cale gets his sister the medicines that Spencer provided him with.]]
* BorrowedBiometricBypass: Of a sort. Unknowingly, Hathaway gets Spencerís biometric pass, sending him on a wild goose chase.
* BrandishmentBluff: Spencer unsuccessfully tries to convince the ESA that he will explode to get out of being cut open. [[spoiler: Unknowingly to Olham himself, it might not have been just a bluff...]]
* ClearMyName: Spencer is trying to prove he isn't an android bomb.
* DeathByAdaptation: [[spoiler: In a type B example, Nelson survived up to the end of the end of the story and was the one to prove that Olham was in fact a bio-bomb, then died along with everyone else in the explosion. In the film, he's accidentally killed by Olham halfway through.]]
* DiabolusExMachina: The film revolves around a man trying to prove that he's not an alien-created replicant of himself with a bomb in his chest. At the climax of the movie, the man and his wife find the alien crash site where he was allegedly killed, and discovers [[spoiler:his wife's body inside the spaceship, proving that his wife was the replicant instead. Then suddenly, in the last few minutes, the authorities that were chasing him through the whole movie discover the man's body as well, proving that he was also a replicant, and the man promptly explodes and kills everyone in the area.]]
* DiscoveringYourOwnDeadBody: A variation on the trope where Dr. Olham becomes a fugitive after he's accused of being a bio-robot infiltration unit sent by a hostile alien race and set to explode when he comes in contact with the Earth's chanceller. [[spoiler:His wife is then revealed to be the real impostor, but then it turns out that ''both'' he and his wife had been replicated when he discovers the real Olham's body.]]
* DomedHometown: The cities are covered by defensive shields to protect them from Alpha Centauri attacks.
* {{Fanservice}}: The somewhat long interrogation scene in which Gary Sinise is shirtless the whole time.
* {{Foreshadowing}}: The forest fire in the countryside is mentioned a couple of times before its relevancy comes about.
* IdiotBall:
** Spencer is accused of being a living bomb sent to assassinate a chancellor making a visit to his city. While escaping the city so he wasnít dissected makes sense, sneaking back into the city to clear his name while the chancellor was still there while Hathaway and company were still on high alert was poor thinking.
** Hathaway was so dead set on Spencer being a bomb that he didnít consider that [[spoiler:Maya might have been a bomb, too.]]
* InspectorJavert: Major Hathaway is chasing Dr. Spencer Olham because he's convinced that Olham is an alien biorobot who killed the original and took on his personality in order to detonate a bomb and kill the Chancellor. He plans to prove that by vivisecting Olham and disarming the explosive, but Olham escapes and spends the whole film trying to prove he's human. [[spoiler:Hathaway turns out to be right, but missed that Olham's wife was also replaced and then fails to consider that both Olhams could have been impersonated, ending in Hathaway's death when the bomb explodes.]]
* KillAndReplace: Dr. Spencer Olham is accused of being an alien biorobot who has killed and replaced the scientist. They plan to prove themselves right by cutting him open to look for a biological bomb. He escapes and spends the rest of the movie trying to prove them wrong. [[spoiler:They're right. Both he and his wife have been killed and replaced with the dopplegangers taking on the originals' memories. When he finds out the truth, the bomb in his chest explodes]].
* NotHisSled: Played with. [[spoiler: In the original story, only Olham is a fake. In the film, his wife turns out to be the fake instead, thus proving that Olham is human. Then it turns out the real Olham really was killed and he is a living bomb.]]
* PostCyberPunk: A CrapsackWorld exists outside the domes, but inside the city, things are pretty nice.
* ReplicantSnatching: The premise is that look-alike copies of key people can be sent after targets, exploding violently once contact is made. The hero is accused of being one such impostor.
* ShootTheShaggyDog: [[spoiler:It ends this way in literally the last few minutes of the movie, with the main character spending the movie on the run and trying to prove that he's not an alien-created replicant bomb. Except that it turns out he ''is'', at which point he promptly explodes and takes every surviving character in the movie with him, save two characters who weren't anywhere near the explosion.]]
* TransferableMemory: The Centauri can completely duplicate a personís memories and personality into their replicas.
* TheReveal: [[spoiler:Two in succession. Dr. Olhamís innocence is proven when Hathaway reveals that his wife has been replaced with the real biorobot sent to assassinate the chancellor. Shortly afterwards they discover the real Olhamís body, as it turns out that both the Olhams were killed and replaced with copies.]]
* TomatoInTheMirror: [[spoiler:Dr. Olham is, in fact, the robo-bomb he's been trying to prove he ''isn't'' for the entire movie. His wife is one, too.]]
* TwentyMinutesIntoTheFuture: Set in 2079, when humanity is at war with Alpha Centauri.
* UtopiaJustifiesTheMeans: Hathaway believes this. So much that he dissected several people before he was able to prove that an android bomb even existed. He also doesnít mind collateral damage when trying to gun down a target.
* WellIntentionedExtremist: Hathaway may be willing to cut potentially innocent people open and gun anyone down in the way, but he is doing it to stop a nuclear size blast from destroying a city.
* WhyAmITicking: This is the basis for the plot of the movie. The main character of the story is suddenly arrested and told that he's not the man he believes himself to be: he's really an ArtificialHuman that is designed to be indistinguishable from the original except that, when he encounters the proper "trigger", he will explode. He doesn't believe it, escapes from his would-be executioners, and tries to find evidence to prove that he isn't an impostor. [[spoiler: At the end of the movie, he discovers that he really is an impostor, and then promptly explodes.]]