The short story Impostor is similar to the film in most respects, in terms of the main idea about the possibility of an artificial alien-created person who looks and acts exactly like our main character, who is going to cause devastation with the bomb hidden inside its chest. Also in terms of the themes of the wanted man who is trying to prove his innocence while everyone is against him, and the uncertainty of not knowing the truth right up to the end. There are a number of minor differences, for example, there is less of an inclusion of Olham’s wife, called Mary in the story. There is also no sign of the small group of renegades headed by Mekhi Phifer in the film. Olham does not go to the hospital and he does not meet his wife in the woods, he goes alone.
There is also a difference in how he escapes his captors, namely the Major (called Peters rather than Hathaway in the story). Olham takes a hover car to work, which picks him up with his work colleague Nelson and Major Peters inside. This then detours out to space and heads for the Moon where he is to be killed. Olham cleverly fools Nelson and Peters into thinking he is about to explode and they jump out onto the surface, leaving him able to make his way back to Earth to try to clear his name.
“I am Olham,” he said again. “I know I am. But I can’t prove it.”
“The robot,” Peters said, “would be unaware that he was not the real Spence Olham. He would become Olham in mind as well as body. He was given an artificial memory system, false recall. He would look like him, have his memories, his thought and interests, perform his job.
“But there would be one difference. Inside the robot is a U-Bomb, ready to explode at the trigger phrase.” Peters moved a little away. “That’s the one difference. That’s why we’re taking you to the Moon. They’ll disassemble you and remove the bomb. Maybe it will explode, but it won’t matter, not there.”
Olham sat down slowly.
(Page 303 of Volume 2 of the Collected Stories)
The short story of Impostor packs a bigger punch than its cinematic adaptation. At only six pages long, Philip K. Dick has to develop an interesting, complicated idea very quickly, and bring it towards its ending, where the truth is revealed. This makes it more exciting and thrilling, whereas, drawn out in to a full-length film, it loses some of its power through additional scenes that feel like they are there for padding. If the filmmakers had built upon the original idea and added some more interesting aspects to it rather than solely relying on it, this would have made for a more enjoyable experience.