Star Trek (1966–1969)
23 user 6 critic

Dagger of the Mind 

Kirk and psychiatrist Helen Noel are trapped on a maximum security penal colony that experiments with mind control and Spock must use the Vulcan mind-meld to find a way to save them.


Vincent McEveety


Shimon Wincelberg (as S. Bar-David), Gene Roddenberry (created by)

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Episode complete credited cast:
William Shatner ... Capt. Kirk
Leonard Nimoy ... Mr. Spock
James Gregory ... Dr. Tristan Adams
DeForest Kelley ... Dr. McCoy
Morgan Woodward ... Dr. Simon van Gelder
Marianna Hill ... Helen Noel
Nichelle Nichols ... Uhura
Susanne Wasson Susanne Wasson ... Lethe
John Arndt John Arndt ... First Crewman
Larry Anthony Larry Anthony ... Transportation Man
Ed McCready Ed McCready ... Inmate
Eliezer Behar Eliezer Behar ... Therapist (as Eli Behar)


After a psychologically disturbed patient from the Tantalus penal colony, Dr. Simon Van Gelder, manages to escape to the Enterprise, Dr. McCoy begins to suspect that something is amiss on the colony. Captain Kirk and Dr. Helen Noel beam down to the planet to investigate. Written by garykmcd

Plot Summary | Plot Synopsis


TV-PG | See all certifications »






Release Date:

3 November 1966 (USA) See more »

Also Known As:

Dagger of the Mind See more »

Company Credits

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Technical Specs


Sound Mix:




Aspect Ratio:

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Did You Know?


A shipping label produced for Star Trek: Deep Space Nine (1993) shows that a (now elderly) Dr. Van Gelder is still in charge of the Tantalus Penal Colony in the 2370s. See more »


Transporter Operator Berkley is credited as an ensign, but the uniform is clearly that of a Lieutenant. See more »


Mr. Spock: Enterprise log, first officer Spock acting captain. I must now use an ancient Vulcan technique to probe into Van Gelder's tortured mind.
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Alternate Versions

Special Enhanced version Digitally Remastered with new exterior shots and remade opening theme song. A highlight of the new special effects is a new exterior shot of the penal colony, replacing a re-used matte painting from another episode. See more »


Referenced in The Red Shirt Diaries: Dagger of the Mind (2014) See more »


Theme from Star Trek
Written by Alexander Courage
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User Reviews

2 August 2018 | by zitacarnoSee all my reviews

This was a very good psychological thriller, dealing with how psychotherapy can be misused in the wrong hands. I remember reading a Sherlock Holmes story in which he observed that "when a doctor goes wrong, he is the first of criminals", and as this episode unfolded I could see one such glaring example. When the deranged Simon van Gelder exploded onto the bridge of the Enterprise and it was found that he was, not an inmate, but an associate of Dr. Adams who had been victimized by the "neural neutralizer", an investigation was imperative. The key to the whole thing was one of the most dramatic scenes in the history of Trek---the first use of the Vulcan mind-meld on a human---and a lot of credit has to go to Dr. McCoy, who for all that he called himself an old-fashioned country doctor was light-years ahead of everyone else; he was the one who pushed the reluctant Vulcan with the urgent "Will it work---or not?" Spock actually performed what I immediately recognized as a quieter version of the Vulcan mind-fusion combined with telepathic hypnosis (and Leonard Nimoy really pulled a fast one on the network censors!); he delivered two quiet, half-whispered suggestions of well-being, relaxation and of weightless suspension, which exerted a calming effect on van Gelder's mind and enabled him to describe his ordeal. And eventually the now-deranged Dr. Adams fell victim to his own nefarious machinations, while van Gelder was restored to sanity by the same Vulcan mind-fusion and took over the direction of the penal colony. +As I watched Spock in action I started to get a new appreciation of what the Vulcans call "wuh tepul t'wuh kashek"---the power of the mind and what it could be capable of. And I recognized the truth of the Sherlock Holmes observation.

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