Star Trek: Season 2, Episode Eighteen “The Immunity Syndrome”

Stardate: 4307.1 (2268)
Original Air Date: January 19, 1968
Writer: Robert Sabaroff
Director: Joseph Pevney

“You speak of the objective hardness of the Vulcan heart,
yet how little room there seems to be in yours.”

Rating: 5 out of 5.

The Enterprise is approaching Starbase 6 for “a much needed period of rest and recreation.” However, before arrival they learn that another starship, the USS Intrepid, has suddenly lost communication. Spock is then overcome by a strange feeling, he senses that the Intrepid has just been destroyed along with all 400 Vulcans aboard. In response to the disappearance, Starfleet orders the Enterprise to divert to sector 39J for a priority rescue mission. Kirk makes the order to head for the Gamma 7A system where billions of inhabitants currently reside, however when they arrive Chekov is shocked to find nothing –the whole star system is gone!

The Enterprise soon finds a strange entity lurking about –is it an interstellar dust cloud? Or a massive hole in space? It looks to be a gigantic amoeba. Rather than flee as Dr. McCoy would have it, Kirk orders the Enterprise probe the entity’s zone of darkness in order to discover what might have happened to the Intrepid. Once inside the boundary layer, a hideous noise causes slowly depleting power loss across the Enterprise, and a crewmen collapses (played by Eddie Paskey who actually previously died in the Star Trek episode “Obsession”). Dr. McCoy tells Kirk that according to the ship’s “life monitors” all aboard are slowly dying. Dr. McCoy begins handing out stimulants. Meanwhile, the Enterprise is also being pulled toward the center of darkness. At Spock’s suggestion, Kirk orders Scotty to thrust forward which causes some people aboard the Enterprise to stabilize, albeit temporarily, however it is not enough for escape.

Kirk convenes his leadership team to discuss (personally, I love these scenes of high-minded deliberation and strategy). Spock suggests the entity is actually an anti-energy field shaped like a giant single-celled amoeba. It is approximately 11,000 miles (not kilometers) in length, 2,000-3,000 miles wide, with an outer layer studded with space debris and waste while the interior consists of protoplasm from a gelatinous layer and a central fluid central mass. Kirk orders Scotty to push forward with an enormous burst of warp speed, using full power, however the sudden power surge causes the entity to suddenly notice the Enterprise. Now, the massive entity begins rapidly drawing the Enterprise closer inward and an unmanned probe is released to investigate.

There are lots of great scenes between Kirk, Spock, Bones, and Scotty deliberating about next steps.  Ideas are discussed, questioned, examined, debated. Spock wants to approach the creature in order to destroy it, while Dr. McCoy wants to examine it scientifically. While time dwindles and power is drained, a decision is made. The sensors aboard the probe are not strong enough and so a manned expedition in the shuttlecraft is required. Al three men –Kirk, Spock, and Bones– play the role of self-sacrificial martyr until Kirk chooses Spock to board the shuttlecraft on what looks to be a suicidal mission. In the shuttlecraft, Spock makes entry into the giant amoeba and heads for the nucleus where he learns that the organism has stored enough energy to reproduce. There are about 40 chromosomes in the nucleus ready to replicate. Spock transmits a broken message about how to destroy the creature from the inside –using the medical knowledge of antibodies invading a cell inside the human body, the Enterprise violently enters the entity and Kirk suggests they use anti-power/anti-matter to deprive the entity of the power it so craves. Before launching the probe, there is a powerful scene of both Kirk and Spock side-by-side delivering highest commendations for one another should they not survive. Naturally, the explosion destroys the creature while the Enterprise and shuttlecraft carrying Spock manage to escape –“Shut up Spock! We are rescuing you.”


Finding a new creature like a giant destructive amoeba poses all manner of ethical quandaries in Star Trek. Should we kill it? Or study the creature? Is it intelligent? Can it feel pain? The higher path is not always clear. However, in this case, the flourishing of life across the galaxy supersedes this single-celled entity’s livelihood –it is a strikingly similar situation to Season 1’s “The Doomsday Machine” and it also reminds us modern viewers of black holes, a somewhat new concept in the 1960s. Ultimately, this massive entity cannot be reasoned with as it swallows up life and energy across the galaxy, and so it must be destroyed. This gives Spock’s suicide mission that much more gravity in this episode even as Dr. McCoy fails to say “good luck” (of course, thankfully Spock narrowly survives).

I thought this was a great episode, especially for being a “bottle episode,” taking place entirely aboard the Enterprise with nothing out of the ordinary for a budgetary reasons (i.e. no shore leave or surface visits). Complete with an exhausted crew facing a difficult ethical problem, as well as one of the most dangerous creatures the Enterprise has encountered (like Melville’s White Whale, it cannot be reasoned with), “The Immunity Syndrome” offers a bounty of themes worthy of consideration. One minor theme concerns the stark contrast between Spock and Bones –Spock’s natural abilities as a half-Vulcan are contrasted with Dr. McCoy’s impressive medical credentials. Both are key assets to the Enterprise and their playful banter comes to an end when Spock makes way for the Galileo in what all expect to be his final mission.


Director Joseph Pevney (1911-2008) is tied with Marc Daniels for most TOS episodes directed. This was his fourteenth and final episode of Star Trek.

Robert Sabaroff (1935-2007) wrote for a variety of shows including Bonanza and The Virginian. He later wrote two celebrated episodes of TNG, as well.

Star Trek Trivia:

  • In this episode, there is a great scene of Kirk addressing the entire crew which allows for a brief montage of crewmen completing various tasks across the ship. It is a helpful reminder that there are hundreds of people working together aboard the Enterprise.
  • The cost of the amoeba creature forced the show to re-use some old Star Trek footage in this episode. This was a cost-cutting “bottle episode.”
  • Vulcan collective memory is mentioned in this episode, and contrary to an earlier comment made by Kirk in the series, the Vulcans do not have a collective memory of being conquered.
  • In the original script, the Vulcan Satak was going to be captain of the Intrepid.
  • At the beginning and end of this episode, Kirk is distracted by a young yeoman crew member.
  • The scene of Spock telepathically reacting to the Vulcans deaths at a distance has often drawn comparisons to Obi-Wan Kenobi in Star Wars reacting to the destruction of Alderaan.
  • Many of the Star Trek staff have remarked on how discipline was breaking down around this time in the show’s production as Gene Coon had left and Joseph Pevney would soon leave too (this was his final episode).
  • Once again, George Takei was away filming The Green Berets and thus John Winston’s character Lt. Kyle takes his place (donning a gold tunic rather than his typical redshirt, though he can be briefly spotted wearing both). Kirk/Shatner repeatedly mispronounces his name as “Cowell.”
  • Music from “The Doomsday Machine” is appropriately used in this episode.
  • When discussing the size of the entity in this episode, characters regularly switch between measuring it in miles or kilometers.
  • The giant amoeba for the original episode was created by Frank Van der Veer of “Van der Veer Photo Effects.” It was created pressing liquids between two thin sheets of glass, giving the appearance of a pulsating amoeba.
  • Eddie Paskey actually previously died in the Star Trek episode “Obsession.” He will also appear again in “Omega Glory.”
  • Before passing through the barrier, Kirk lists off all the crewmen worthy of praise along with their ranks. He mentions Dr. McCoy as a “lieutenant commander” –the only time his rank is mentioned in TOS.
  • This was the first episode to originally feature a Paramount Television logo rather than Desilu logo –Delisu had been just sold to Paramount.  

Click here to return to my survey of the Star Trek series.

2 thoughts on “Star Trek: Season 2, Episode Eighteen “The Immunity Syndrome”

  1. I always remember enjoying this episode mainly for the impressive effects for the space amoeba, the pre-CGI version that is, even though the CGI updates are impressive too. As for how much of classic Trek saw the Enterprise crew forced to resort to kill-or-be-killed in episodes like this, it’s a difficult thing to take in today after how much Trek has matured over time. But this episode can still have some of the best Enterprise crew drama for Trekkers to reflect on. Thank you for your review and trivia.

    Liked by 2 people

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