An alien spaceship lands in the wilderness, and the military sets up loudspeakers. They then call out on the saucer inhabitants to come out, promising that they won't be harmed.
General Crawford is woken up by an alert, and intelligence agent Leon Chambers comes in. Chambers says that Crawford should call off his plan to start shooting, warning that it would be a critical mistake. Crawford refuses, saying that if the creatures are dangerous then they could pose a threat. Chambers insists that not everyone has an ulterior motive, and Crawford points out that the aliens wiped out a patrol. The intelligence agent says that it's enough to start a war over and the aliens may have been frightened, but Crawford warns that he can't afford to play games. If they haven't heard from the aliens by 0700, they'll destruct. Chambers warns that the explosion will destroy half of the state, since the ship contains fissionable material. Crawford gives Chambers permission to go ahead with his plan, but figures that no one would volunteer once they find out what the job involves. Chambers says that he has his man.
In a cantina, Louis Mace is swatting flies. A man comes in and a man in a suit glances back and forth with the newcomer. The newcomer sits down next to Louis and draws a gun, covering it with a newspaper. He says that he wants to talk outside, but Louis refuses. When the man grabs Louis' arm, Louis chokes him with the handle of the fly swatter. The other man runs out, and Chambers comes in as Louis' victim collapses dead. The cantina guitarist's guitar is smashed in the fight, and Louis offers him what money he has but realizes that it's not enough.
Louis sees Chambers and sits down at the bar. Chambers joins him and asks who they were, and Louis tells him that they were old enemies. He figures that Chambers and his superiors would want him again, and figures that no one else would do it so Chambers came to him.
In the U.S., Chambers and Dr. Tillyard play a film of the spaceship showing humanoid aliens emerging. The aliens didn't display hostility at the time, but they later killed a patrol sent to investigate. Crawford comes in and says that he's amazed at the report about Louis. He complains that Louis is a derelict, living in the wilds of Mexico, and Chambers explains that Louis used to work for them but his identity was exposed and compromised.
Louis is sitting in the shadows and introduces himself to Crawford. Crawford makes no apologies for what he said, and asks if Louis thinks that it's possible to pose as one of the aliens. Louis says that he doesn't know what he volunteered and doesn't care. The mission calls for an experienced agent, and Louis welcomes the new experience. They begin the film again and Crawford says that he doesn't know what the aliens are and they can't blow up the ship without risking a nuclear explosion. There only option is to get an agent inside with a hidden audio camera, and let him transmit back everything so they can make an evaluation. To infiltrate the spaceship, Louis has to become one of them. Intrigued, Louis studies the footage and Chambers says that Tillyard has been working with the Space Agency to adopt men to environments. Tillyard thinks that he can transform Louis and bring him back.
Tillyard takes the others to a lab and shows them how he altered a monkey to survive in an Arctic environment. Crawford warns that they can't guarantee Louis' safety, and he says that he understands. The general says that they have to start immediately before the public learns about the aliens and panics, and Louis points out that he already agreed.
Tillyard begins Louis' transformation by taking a blood sample. The doctor admits that Louis is an extraordinary man, pointing out that he isn't risking his life. Louis says that he has a unique capability to survive, and he'll be just as foreign to the aliens as they are to him.
Later, Chambers tells Louis where the aliens are and explains that they'll provide a cover story for the ex-agent. They're filling the air with talk of having spotted another alien in the area, and then chase him. Louis will join the aliens and say that he crashed there long ago and doesn't remember anything of his past. There's an audio camera hidden in a replica of the aliens' equipment, and a transmitter so that they can signal Louis to get out if they decide to destroy the spaceship. Tillyard begins the next step of the transformation and Louis invites Tillyard to explain what he's doing if it will reassure him. The doctor says that they obtained a sample of the aliens' DNA from a scraping under one of the dead soldier's fingernails. He will then recreate the structure in Louis, changing his entire body except his brain. Afterward they will reverse the process using the DNA from the blood sample Tillyard took earlier. Louis contemplates the tape with the data and wonders if it would be a heavy loss if it was destroyed.
Before Tillyard begins the procedure, Tillyard tells Louis that he can reconsider if he wishes. Louis says that he's an instrument of action, not a hero. All he has is what he can do. Tillyard anesthetizes Louis, who mumbles about how he broke the guitar and wants to build something for a change. Chambers assures him that he'll be doing something worthwhile, but Louis isn't convinced.
Under ultrasonic treatment, Tillyard transform Louis into an alien. Once he's done, Chambers calls over the intercom into the chamber. Louis makes a giggling noise and stares at his transformed hands, then comes out. He finally speaks, saying that they look peculiar to his new eyes. He takes the tape with his DNA data on it and giggles again.
Later, Louis approaches the spaceship as the military chases him toward the spaceship and broadcasts their pursuit over the radio. Louis reaches the spaceship and goes inside the open hatch. Inside, Chambers and the others see through Louis' camera as he looks around the interior. One of the aliens trains a beam on Louis, surrounding him in a force field. The lead alien explains that Louis is imprisoned and then chuckles, and says that it's a good impersonation. He says that they know he's a human, and the humans would destroy them when they've done them no harm. The alien points out that they only killed the soldiers in self-defense, and Louis points out that he couldn't kill one of his kind. He says that he feels like one of them and knows what the equipment is. Louis points out the various pieces of equipment and describes their function, and the aliens' planet. He realizes that it was the alien leader's DNA that they recovered from the dead soldier, and the leader says that they'll discuss Louis' fate and return.
Crawford and the others listen and watch on the monitor, and Tillyard admits that he doesn't know if Louis' brain was altered. Chambers warns that they may be losing their agent through defection.
The two aliens return and the leader tells Louis that they've decided that they won't harm Louis or anyone else. They only want to return home safely, but insist that Louis comes with them. The aliens were instructed not to leave any trace of themselves for fear someone would use their advanced knowledge for aggressive purposes. Because Louis is one of them, they can't leave him on Earth. The leader says that there's no mistrust or fear of war on their planet, and Louis loudly says that they have no atomic weapons. The aliens affected the military instruments to thwart any attack, and say that they will leave as soon as they repair their spaceship. Louis tells them that he was an agent and belongs on Earth, and he has a life to go back to. The leader asks if it's a better life than what they offer, and if Louis has accepted his life or is resigned to it. They want Louis to want to share their life, and Louis giggles and says that it's a joke on Chambers, but he'll understand.
Louis tells them that he wants to come, and the aliens drop the force field. The leader takes him to help them complete the repairs, while Chambers says that it's all right if Louis goes with them. Crawford insists that the aliens would know all about their weaknesses and could blackmail them, and prepares to call an artillery strike on the spaceship. Chambers objects and Tillyard points out that the attack will kill Louis, but Crawford says that they can't trust the unknown. The agent hopes that if he activates the buzzer, it will trigger Louis' instinctive reactions to complete his mission. After a moment, Crawford agrees.
Chambers sends the signal, and Louis grabs a weapon and kills one of the aliens. The dying alien falls onto Louis, knocking the gun out of his hands. The leader climbs out of the spaceship and Louis recovers the gun and chases him through the forest. Crawford prepares to send some help, but Chambers tells him that it won't be necessary.
Louis finally catches the leader and prepares to kill him. However, after a moment he refuses and says that the alien was right. Louis asks if the leader would still have him come with him, and the leader says that he would welcome a friend. Crawford calls to Louis over the loudspeakers, ordering him to come back. Louis refuses to return, saying that he's neither Louis or an alien, but he knows that they're telling the truth. Now he'll go to a planet where he no longer needs to be a chameleon. Louis destroys the camera and goes back to the spaceship with his new friend.
Crawford prepares to order an artillery strike, but then tells his men that he doesn't want the spaceship interfered with. The three men go out and watch the spaceship depart.
Written by Gadfly on Jan 7, 2018