The 1950 short story “To Serve Man” by Damon Knight is a science fiction version of the classic proverb caveat emptor, buyer beware. The aliens in the story, the Kanamit, make a wonderful promise to the people of Earth but their actual intentions are the opposite.
Peter, the narrator of “To Serve Man” describes the arrival of three members of the Kanamit delegation at an United Nations meeting. He comments on the appearance and behavior of the aliens and relates,
[The Kanamit] seemed perfectly at ease. That, along with their humor, made me like them. They said quite simply that they wanted to help us. I believed it. As a U.N. translator, of course, my opinion didn’t matter. But I thought they were the best thing that ever happened to Earth.
This initial description immediately raises important details: the aliens know how to present themselves to humans in a disarming way, they start out with a simple sales pitch as a hook, and that Peter already suspends his critical thinking abilities by dismissing his role in the experience.
A few of the delegates however have retained their skepticism and need proof. The French representative, repeating a point raised by the Soviet delegate, inquires about the motivations of the Kanamit, because they are making promises without asking for anything in return. After passing a lie detector test, one of the aliens delivers the full promise:
I hope that the people of Earth will understand and believe that our mission is simple. It is to bring you the peace and plenty that we enjoy. We have, in the past, brought it to other races throughout the galaxy. When your world has no more hunger, no more war, no more suffering—that will be our reward.
The Kanama who relates this message passes the lie detector test. The altruism and the implied experience and efficiency with which the promises will be carried out, impress the delegates.
However, the narrator’s friend Grigori does not trust the Kanamit, calling the meeting a circus and a joke. Peter criticizes Grigori for his suspicions, in particular Grigori’s comment that the individual Kanama who spoke looks like “it ate the baby.” Meanwhile, the Kanamit assist humanity with a new power source, increased agricultural yield, and technology to end war. It seems Earth will now become a paradise of peace and prosperity.
But what follows is one of the classic twists of science fiction: Peter and Grigori get jobs at the embassy established for the Kanamit, work on translating their book How To Serve Man, only to find the Kanamit’s promise was a ruse. For all the good things they’ve promised and done, the Kanamit are revealed to be aliens who are hungry, on a mission to consume their way through the galaxy.
It’s interesting to note a significant contrast between Knight’s original story and the screenplay adaption by Rod Serling for The Twilight Zone television series. The narrator in Knight’s story describes the Kanamit as “fat, piglike creatures in green shorts” and notes that people may have expected aliens to look like angels. Serling’s screenplay follows through on that idea by depicting the Kanamit as tall, dignified beings in white robes, perhaps emphasizing that no matter what the messenger looks like, a customer should think before buying into a plan.