Before I begin let me say that the story I am thinking of is not "Hostess" by Isaac Asimov. The premise is very similar though.

In this story, some humans are captured and studied by an alien species. When one of the humans gets sick and dies, the aliens blame the other human for his death. Once they determine how the human died, they reveal that humans are the only species they have studied that die of natural causes.

Specifically, the aliens explain that most species have cells that grow forever similar to the concept humans call cancer.

I may have heard a radio adaption of this story on X Minus One.

  • is not "Hostess" by Isaac Asimov - which is too bad, because it's brilliant. A woman scientist in a story in the 1950s? People smoking pipes? Commented Dec 19, 2019 at 20:54
  • @MauryMarkowitz What's so special about a woman scientist in a story in the 1950s? What about Caroline Martin in Cosmic Engineers (Simak, ASF, 1939)?
    – user14111
    Commented Dec 20, 2019 at 0:34
  • 1
    Is not the story in @user14111 's answer the one you're thinking of? It's the one I thought of while reading your question.
    – NomadMaker
    Commented Jan 17, 2021 at 0:22

1 Answer 1


You may be thinking of "Knock", a short story by Fredric Brown which has its own Wikipedia page. It was first published in Thrilling Wonder Stories, December 1948, which is available at the Internet Archive, as are the Dimension X and X Minus One radio adaptations.

The alien Zan are invaders who have killed all human and animal life on Earth except for a few specimens they saved for their zoo. They have never heard of natural death, and are baffled when some of their specimens die. (However, the dead specimens are animals, not humans, and there is no mention of cancer. So maybe you're thinking of another story, or maybe you're mixing up two different stories.) In the excerpt below, one of the human specimens is visited by a Zan whom he calls "George":

Walter Phelan called out, "Come in," and the door opened. It was, of course, only a Zan. It looked exactly like the other Zan; if there was any way of telling them apart, Walter hadn't found it. It was about four feet tall and it looked like nothing on Earth—nothing, that is, that had been on Earth before the Zan came here.

[. . . .]

"There is some-thing we do not un-der-stand. Two of the oth-er an-i-mals sleep and do not wake. They are cold."

"It happens in the best-regulated zoos, George. Probably not a thing wrong with them except that they're dead."

"Dead? That means stopped. But noth-ing stopped them. Each was a-lone."

Walter stared at the Zan. "Do you mean, George, that you do not know what natural death is?"

"Death is when a be-ing is killed, stopped from liv-ing."

Walter Phelan blinked. "How old are you, George?" he asked.

"Six-teen—you would not know the word. Your pla-net went a-round your sun a-bout sev-en thou-sand times. I am still young."

Walter whistled softly. "A babe in arms," he said. He thought hard for a moment. "Look, George, you've got something to learn about this planet you're on. There's a guy down here who doesn't hang around where you come from. An old man with a beard and a scythe and an hourglass. Your vibrations didn't kill him.

"What is he?"

"Call him the Grim Reaper, George. Old Man Death. Our people and animals live until somebody, Old Man Death, stops them from ticking."

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