17 user 6 critic


Capt. Kirk obsessively hunts for a mysterious cloud creature he encountered in his youth.


Ralph Senensky


Gene Roddenberry (created by), Art Wallace




Episode complete credited cast:
William Shatner ... Capt. Kirk
Leonard Nimoy ... Mr. Spock
DeForest Kelley ... Dr. McCoy
Stephen Brooks Stephen Brooks ... Ensign Garrovick
James Doohan ... Scott
Nichelle Nichols ... Uhura
Jerry Ayres Jerry Ayres ... Rizzo
Majel Barrett ... Nurse Chapel
Walter Koenig ... Chekov


Captain Kirk is haunted by a creature from his past when conducting a mining survey on a planet. He first encountered it as a lieutenant aboard the U.S.S. Farragut and blames himself for freezing in a moment of crisis, causing the death of many crewmen. The creature is a cloud-like, gaseous being that lives on the red blood cells found in humans. Obsessed by his desire for revenge and to erase the memory of 11 years ago, he pursues the creature relentlessly, putting in jeopardy an assignment to collect essential medical supplies. Written by garykmcd

Plot Summary | Plot Synopsis


TV-PG | See all certifications »


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Release Date:

15 December 1967 (USA) See more »

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Technical Specs


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Did You Know?


The only episode to have a security guard as the central story. See more »


In the first scene, Spock phasers off a sample of rock, which has been clearly pre-cut to fall off on command. See more »


Capt. Kirk: I'm aware of the situation, engineer, and I'm getting a little tired of my senior officers conspiring against me. Forgive me. Perhaps I shouldn't have used the word "conspire."
Scott: Agreed, sir.
See more »

Alternate Versions

Special Enhanced version Digitally Remastered with new exterior shots and remade opening theme song See more »


Referenced in Star Trek: First Contact (1996) See more »

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User Reviews

It can't possibly exist...but it Does!
11 October 2006 | by BogmeisterSee all my reviews

Will we ever be free of our monsters, even in the 23rd century? This episode says of course not and, especially in view of what we've seen of the 24th century on the TNG show and other spin-offs, there will always be space-age demons and goblins to terrorize us. Following up on commodore Decker's Ahab-like role on "The Doomsday Machine," now it's Kirk's turn to confront and obsess about his personal devil. Yet, his nemesis, in a key revelatory point of the story, is not some unthinking machine; it really is a predatory monster, killing off red-shirts left and right, like a space-faring shark with malicious tendencies (it breaks the record of red-shirt deaths in "The Apple," even if one of these happen off-screen). Shatner gets to show a bit more range than usual here; he doesn't go off completely half-cocked or deranged, but there's enough edginess in him here to warrant McCoy & Spock briefly teaming up against him, recalling the key scene in "The Conscience of a King."

The story does drive home one point probably a couple of times too many: that Kirk's guilt over not killing the creature years earlier is groundless. McCoy's scene with Kirk, where he points out his captain's possibly overly obsessive approach to the problem, is very good. But then we have Spock going over this ground over and over, it seems, both with Kirk & ensign Garrovick, another guilt-ridden character. Yes, the parallels of what's currently happening in this episode and events of several years ago on the starship Farragut are somewhat eerie, but enough already, Spock. Stop beating the audience over the head with it. Despite this clumsy aspect to story construction, it's a fairly exciting, suspenseful riff on the dangers lurking in outer space, even in Trek's quasi-utopia future. Much later, Captain Picard would be accused of Ahab-like behavior in "Star Trek-First Contact"(96) involving, what else, the Borg. This seems a prevalent theme among starship captains of the Trek mythos.

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