The Enterprise encounters a gigantic energy draining space organism that threatens the galaxy.



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Episode complete credited cast:
John Winston ...


The Enterprise is sent to investigate the disruption of the Gamma VII-A solar system and the destruction of the U.S.S. Intrepid, staffed solely by Vulcans. When they arrive they find a large dark mass floating in space that is draining energy from everything around it, including the Enterprise. Drawn into the mass, they find a huge amoeba-like creature and Kirk must decide which of his two friends, McCoy or Spock, to send into it aboard a shuttle craft on a mission of no return. Written by garykmcd

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Release Date:

19 January 1968 (USA)  »

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1.33 : 1
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Did You Know?


47 reference: Spock states the shuttles' shields will last only 47 minutes See more »


As they were approaching the dark cloud, Uhura said she can't receive communication from Star Fleet due to interference which is getting worse, however, moments later Kirk asks Uhura to notify Star Fleet and Uhura reports that the transmission was complete, though interference prevented contact earlier. See more »


Capt. Kirk: Spock?
Dr. McCoy: What is it, Spock? Are you in pain?
Mr. Spock: Captain, the Intrepid. It just died. And the four hundred Vulcans aboard, all dead.
See more »


Referenced in Star Wars: Episode IV - A New Hope (1977) See more »

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User Reviews

A Fantastic Voyage
6 August 2006 | by (New York City) – See all my reviews

The plot of this great episode, insofar as the antagonist goes, at least, is something of a combination of the then-contemporary Jules Vernish Sci-Fi film Fantastic Voyage (1966) and past Star Trek episodes of more exotic extraterrestrial life forms, such as Obsession, which immediately preceded The Immunity Syndrome if you follow the production rather than the broadcast order.

That doesn't mean that this is a rip-off (not that I'd deduct points from it just for that fact alone, anyway), but just a very Trekkian way of doing an interesting idea. And at any rate, as with most Trek episodes, what really makes it work are the character dynamics (stemming from both the writing and the performances).

Especially beginning in the second season, Star Trek writers (surely including creator Gene Roddenberry and under his guidance) had a lot of fun exploring a yin-yang dynamic between Spock and Dr. McCoy. Spock, as even many people who aren't Trek fans know, represents a "cold", logical way of looking at everything, although Trek fans know that he's much more complicated than that (providing a bit of his yin-yang opposite within himself), and it's not just because he's half-human--other Vulcans are more complicated than that, too. Whereas McCoy, emphasizing his "I'm just a country doctor" attitude, is often highly emotional--ready to fly off the handle at the drop of a deflector shield, and ready to make a sarcastic crack the moment he sees Spock, at least. The presence of his yin-yang opposite within himself can be more difficult to see, but surely it's in his vocation and vocational activities.

The Immunity Syndrome is as good a place as any in the second season to watch that yin-yang tension and harmony between Spock and McCoy unfold, and it's brilliantly set up and justified here by both an event (the fate of the Vulcan ship) that immediately proceeds our main dilemma and the facts of the main dilemma as they are figured out.

This episode also hits you in the face with a surprising side of Spock that was shown many times earlier, but usually in a way that seemed less contradictory--he basically has psychic abilities, to an extent where some humans around him are highly skeptical of the skill, and where it's obvious that at least as humans and Star Trek viewers understand the mechanisms at this point, the abilities aren't exactly logical.

At any rate, for various reasons, this episode should keep you on the edge of your seat for much of its length. The antagonist, which at first cleverly seems something like a black hole, embodies a fascinating idea, and something that would be very dangerous if it could be true. There are gripping sacrifices being made, near impossible technical/technological difficulties to overcome, and the situation has everyone psychologically strained to a near breaking point.

And there's something else worth watching out for in this episode, especially for those who like to point out some of the shows often-funny quirks on a meta-level, since it's one of the best examples of this--just why did Starfleet not have the foresight to install seatbelts or harnesses on its ships and shuttles? The Immunity Syndrome features many great scenes of actors flailing about, throwing themselves on the floor, and in one case, even doing an impressive flip (watch for a minor character in the background on the bridge towards the end of the episode) as the camera rocks back and forth to represent turbulence.

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