The film takes place in the year 2079. Forty-five years earlier, Earth was attacked by a hostile and implacable alien civilization from Alpha Centauri. Force shield domes are put in place to protect cities, and a totalitarian global military government is established to effect the war and the survival of humans. The Centaurians have never been physically seen.
The film follows Spencer Olham, a designer of top-secret government weapons. He is arrested by Major Hathaway of the Earth Security Administration (ESA), 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, whom he was scheduled to meet. 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, which can only be detected by dissection or a high-tech medical scan, since it only assembles itself when it gets in proximity to its target. Detection via the special scan works by comparing against a previous scan, if there was one.
Major Hathaway begins interrogating Olham. As he's about to drill out his chest to find the bomb, Olham breaks loose and escapes, accidentally killing his friend Nelson in the process. With the help of underground stalker Cale, Olham avoids capture and sneaks into the hospital where his wife Maya is an administrator to get the high-tech scan redone and prove he's not a replicant. But the scan is interrupted by security forces before it can deliver the answer.
Olham and his wife are eventually captured by Hathaway's troops in a forest near an alien crash site, close to the spot where they spent a romantic weekend just a week or so 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 imposter, but as his men move debris away from the Centauri ship, the real Spencer's body is revealed. At that moment, Olham realizes aloud that he really is a replicant, and the 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 fiery nuclear explosion.
In the final scene, the news announces that Hathaway and the Olhams were killed in an enemy 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.Gary Sinise as Spencer Olham
Madeleine Stowe as Maya Olham
Vincent D'Onofrio as Hathaway
Mekhi Phifer as Cale
Tony Shalhoub as Nelson Gittes
Tim Guinee as Dr. Carone
Gary Dourdan as Captain Burke
Lindsay Crouse as Chancellor
Clarence Williams III as Secretary of Defense (uncredited)
Elizabeth Pena as Midwife
Shane Brolly as Lt. Burrows
Golden Brooks as Cale's Sister
Ted King as RMR Operator
Rachel Luttrell as Scan Room Nurse
The film adaptation was originally planned to be one segment of a three-part science fiction anthology film titled Light Years, but was the only segment filmed before the project fell apart. The other shorts were to be adaptations of Isaac Asimov's story "The Last Question" by Bryan Singer and Donald A. Wollheim's story "Mimic" by Matthew Robbins. "Mimic" had already been adapted into a film of the same name, but with a different script.
The short was originally written by Scott Rosenberg, with revisions by Mark Protosevich and Caroline Case. When it was decided to expand the short into a feature-length film, additional scenes were written by Richard Jeffries, Ehren Kruger, and David Twohy.
Burn areas in Running Springs, California, were used to create the space craft crash site. Sets were constructed in Angeles National Forest and in numerous areas around Los Angeles. Most of the interiors were built on stage in Manhattan Beach, including a two-story hospital and 3-story pharmacy, and a commuter transport station with articulated commuter "bugs". Other filming locations included the Coachella Valley.
The movie was made on an estimated $40 million budget.
Impostor received negative reviews from critics. Rotten Tomatoes gives the film a score of 22% based on 91 reviews. Metacritic gives the film a score of 33% based on 26 reviews.
James Berardinelli of ReelViews gave the film two and a half stars (out of four), saying "there are a few moderately diverting subplots and the storyline eventually gets somewhere," but added that "Impostor wears out its welcome by the half-hour mark, and doesn't do anything to stir things up until the climax. You could spend the entire midsection of this movie in the bathroom and not miss much." William Arnold of the Seattle Post-Intelligencer gave the film a mildly positive review, praising lead actor Gary Sinise's ability to "hold the film together and provide a strong, sympathetic human focus. The movie's atmosphere has a very definite Blade Runner feel." Maitland McDonagh of TV Guide gave the film three stars out of four, saying it packed "a real emotional wallop," but suggested that it would have worked better as the 40-minute short film it was originally intended to be.
Keith Phipps of The Onion's A.V. Club gave the film a negative review, saying that "it essentially uses the setup of [the story] as a bookend to one long, dull chase scene." Robert Koehler of Variety also criticized the film, calling it "a stubbornly unexciting ride into the near future."
A. O. Scott of The New York Times offered a sardonic view of the movie's "dark view of the future" ("a badly lighted one, that is"), of the editing ("pointlessly hyperkinetic"), and of the "twist" ending ("meant to be clouded with ambiguity, but really it is unequivocally happy because it means the movie is over").
The film earned a little over $6 million at the box office in the United States and Canada, with the estimated worldwide of over $8 million, thus making it a box office failure.