Harold's Old Time Radio: "Future Tense 74-05-13 (05) Knock"

Aired: January 22, 2026
Source: Classic radio adaptation of Frederick Brown’s story "Knock"
Episode Theme:
A chilling science-fiction fable about the last humans on Earth, an alien zoo, immortality, and the quirks of human—and nonhuman—nature.

Episode Overview

This episode of Harold's Old Time Radio presents "Knock," adapted for radio from Frederick Brown’s famous short story, encapsulating both existential horror and sly humor. The narrative opens with the classic line: “The last man on Earth sat alone in a room. There was a knock on the door”—then quickly expands into a tale of alien invasion, captivity, and what it means to be human. Centered on Walter Phelan, an anthropology professor, and Grace Evans, another captive, the story explores their interactions with the logically motivated, near-immortal alien conquerors called the Zahn, touching on mortality, resistance, and—ultimately—renewal.

Key Discussion Points and Insights

1. The Premise and Setting

• The narrator poses a question with an air of suspense: “Suppose you were the last man alive on Earth—and suddenly there was a knock on the door. What knocked on the door? …Your mind supplies something vaguely horrible. But it isn’t horrible, really.” (00:46–01:33)
• The episode immerses listeners into a future Earth after an alien invasion has wiped out most life, sparing only selected "specimens" for a cosmic zoo.

2. First Encounter with the Aliens

• The protagonist, Walter Phelan, awakens to find himself questioned by Azan/“George,” a representative of the Zahn, who matter-of-factly explains:

  “The Zahns have annexed your world.” (03:52)
  “There is no longer any use for large numbers of lower life forms. Therefore, we have dispensed with them.” (04:09)

• Walter learns he is the last man on Earth, and his captor refers to humanity as “lower life forms." The Zahn’s cold detachment—contrasted with Walter’s mild sarcasm—sets a darkly comic tone.

3. The Zoo Arrangement and Alien Logic

• Walter deduces he is in a zoo, displayed for the Zahn:

  “I’m in a zoo, right?” (06:47) “Face the bars and perform for the people. I mean, for the Zahns.” (07:02)

• Aliens show a rudimentary grasp of biology, unaware of concepts like “natural death” and “aging.”

4. The Mistake of Immortality

• The Zahn’s logical worldview is challenged when animal specimens begin dying unexpectedly:

  “George, do you mean to tell me that you don’t know what natural death is?” (08:02)

• Walter explains that unlike the Zahn, humans and animals age and die naturally. The aliens are unsettled:

  “George, you’ve made a mistake, and I don’t think there’s very much you can do about it.” (09:13)

5. The Human Response: Detachment and Resistance

• Grace and Walter discuss their predicament, debating whether humanity should persist as zoo specimens:

  “The least favor we can do the human race is to let it end with us.” (12:48)

• Grace counters, calling for resistance:

  “We just can’t end it by giving up. We’ve got to keep on fighting.” (18:39)

6. Escalation: Alien Torture and Human Resilience

• The Zahn attempt to extract the “secret” of death from Walter via escalating "vibration" torture, but Walter stubbornly resists:

  “You will tell us how you stop these animals.” (21:52)

• Ultimately, the aliens calculate Walter won’t break; they switch to targeting Grace.

7. The Turning Point—A Deadly Solution

• Desperate to save Grace, Walter promises to reveal the “secret” and requests to see the recently deceased animals.
• Afterward, Walter confides to Grace:

  “After a while, I told them what they wanted to know.…As George pointed out, it seemed to be the logical thing at the time.” (24:30–24:41)

8. Death Comes for the Zahn

• Suddenly, a Zahn dies:

  “Zahn has been stopped.…That is correct.” (25:34–25:41)

• Walter explains their immortality is not suited to Earth; “old man Death” gets everyone here. More Zahn begin dying, causing panic:

  “You came to the wrong planet, George. Your immortality doesn’t go down here.” (27:20)

9. The Aliens Depart

• The aliens decide Earth is too dangerous, abandoning the planet:

  “We will leave your planet.…It is not safe for the Zahn, Walter.” (27:42–27:48)

• Walter and Grace are left alone, the true last humans.

10. The Real Secret and the Garden of Eden

• Walter reveals to Grace how he manipulated the Zahn:

  “I told them it was love that made the world go around. Having lost his mate, Donald [a rabbit] would die immediately unless he had affection and constant petting.…Then I let the Zahn take over with the animal in the next cage.…It’s a rattlesnake. The Zahn’s metabolism made it impossible for them to die of old age, but I had a hunch they could be poisoned.” (29:03–30:46)

• By tricking the aliens into exposing themselves to Earthly hazards, Walter secures freedom.

11. A New Beginning

• The episode ends with Walter and Grace, echoing Adam and Eve:

  “Yes, it’s the Garden of Eden all over again.” (32:10)

• The story closes on a humorous and romantic note as Walter flirts:

  “I wouldn’t love you if you were the last man on earth.”
  “That’s exactly what I am.” (32:42–32:47)

Notable Quotes & Memorable Moments

• Narrator:

  “Suppose you were the last man alive on Earth…suddenly there was a knock on the door. What knocked on the door?” (00:46–01:33)

• Walter (to Zahn):

  “I gotta call you something. Do you mind if I call you George?” (05:23)

• Zahn/George:

  “That is characteristic of low life forms.” (05:43)

• Grace (on resistance):

  “If there was any good in man, it was that he kept on struggling against nature—at least he kept on fighting for what he thought was right.” (18:18)

• Walter (explaining death):

  “You came to the wrong planet, George. Your immortality doesn’t go down here. He can stop you but you can’t stop him.” (27:20)

• Walter (on his trick):

  “It was the snake that killed the two Zahn. If they never knew what bit them.” (30:57–30:59)

• Grace (humor):

  “I wouldn’t love you if…if you were the last man on earth.”
  Walter: “That’s exactly what I am.” (32:42–32:47)

Key Timestamps

• The Two-Sentence Horror Premise: 00:46–01:33
• First Alien Interaction: 02:54–05:59
• Revelation: The Human Zoo: 06:44–07:02
• Understanding Mortality: 08:02–09:13
• Walter & Grace’s First Meeting: 09:52–10:44
• Debate over Human Resistance: 12:48–13:11
• “Torture” Sequence: 20:20–22:33
• Zahn Deaths and Retreat: 25:34–27:48
• Walter Reveals the Real Secret: 29:03–30:46
• Final Adam-and-Eve Humorous Exchange: 32:42–32:47

Episode Tone

While the premise is existential and gently horrific, there is a constant undercurrent of sardonic humor—much of it delivered in Walter’s dry banter and the alien George’s literalism. The show mingles suspense, speculative fiction, and sly romance, ending with hope and a wink.

Conclusion

“Knock” stands out as a gripping, darkly whimsical meditation on what it means to be human, the inevitability of death, and the irrational powers of affection and resistance. Through a clever blend of suspense, wit, and poignancy, this broadcast delivers both chills and a smile—reminding listeners that in the darkest future, humanity endures, sometimes against all odds.