General Information
Director: Vincent McEveety
Writer: S. Bar-David
Cast: William Shatner, Leonard Nimoy, James Gregory, DeForest Kelley, Morgan Woodward, Marianna Hill, Nichelle Nichols, Susanne Wasson, John Arndt, Larry Anthony, Ed McCready, and Eli Behar
Composer: Alexander Courage
Air Date: 11/3/1966
Stardate: 2715.1
Production #: 6149-11
Overview
Dr. Simon Van Gelder (Morgan Woodward), a mentally disturbed patient from the Tantalus Penal Colony, beams aboard the Enterprise during a routine cargo drop. While investigating the incident, Captain Kirk and Dr. Helen Noel (Marianna Hill)—a psychiatrist and former flame of Kirk—grow suspicious of Dr. Tristan Adams (James 
Gregory), whose neural neutralizer could be responsible for Van Gelder’s condition.
The first Star Trek offering to feature the Vulcan mind meld, “Dagger of the Mind” should be requisite viewing for fans of the original series. Notably, a compelling amount of narrative tension is present from start to finish, thereby allowing the audience to easily invest in the central conflict of this episode.
Pros
Morgan Woodward (known to Star Trek fans for his portrayal of Captain Tracey in “The Omega Glory”) should be commended for his performance,
the tormented quality of which reinforces the credibility of Simon Van Gelder’s predicament. Specifically, by contorting his face, shouting at the top of his lungs, and repeatedly stopping in midsentence while attempting to warn Spock and McCoy of the danger posed by Dr. Adams, Van Gelder comes across as a genuinely conflicted person who, despite suffering permanent psychological damage, only wishes to prevent others from experiencing harm.
Cons
No explanation is provided for why Dr. Adams—presumably a dignified, benevolent medical practitioner at some point in the past—turns into a sadistic madman while assigned to the Tantalus Penal Colony.
Also never explained, Kirk remains visibly unscathed after the neural neutralizer is tested on him—much in contrast to Van Gelder, who becomes a raving lunatic upon exposure to the device.
Analysis
Possibly a veiled critique of the psychiatric industry, “Dagger of Mind” would seem to imply that treatment methods of an extreme or controversial nature (e.g., shock therapy) should be employed only as a last resort.
Concluding Comments
“Dagger of the Mind” is a thrilling, suspenseful, and occasionally thought-provoking episode. Star Trek enthusiasts may therefore enjoy this entry, logical and continuity flaws notwithstanding.
Overall Quality: 8/10
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This was a good, suspenseful psychological thriller, and as I watched it I thought back to a Sherlock Holmes story in which he observed that “when a doctor goes wrong, he is the first of criminals”. I recognized the truth of that statement, and I have often wondered what makes such people go wrong in this way. I also got a new and deep appreciation of what the Vulcans call “wuh tepul t’wuh kashek”—the power of the mind and what it could be capable of—as I watched and got caught up in the scene where Spock performed the first Vulcan mind-meld on a human; I immediately recognized it as a quieter version of the powerful and dramatic Vulcan mind-fusion coupled with telepathic hypnosis, which calmed van Gelder’s mind and enabled him to describe his ordeal (and at the end restored his sanity). Let me add that a lot of the credit has to go to Dr. McCoy for pushing the reluctant Vulcan with the urgent “Will it work—or not?”