Star Trek (1966): S01E09 – Dagger of the Mind


“Dagger of the Mind” is the ninth episode of the first season of the American science fiction television series, Star Trek.

In the episode, the Enterprise visits a rehabilitation facility for the criminally insane where the chief doctor has been using a device which destroys the human mind.

This episode introduces the Vulcan mind meld.

The title is taken from a soliloquy by the title character in William Shakespeare’s play Macbeth.


The Enterprise, commanded by James T. Kirk, makes a supply run to planet Tantalus V, a colony where the criminally insane are confined for treatment. The facility’s director is Dr. Tristan Adams, a psychiatrist famous for advocating more humane treatment of such patients. After the Enterprise delivers supplies and receives cargo from Tantalus, a man emerges from one of the containers taken aboard and assaults a technician. Reaching the bridge, the intruder demands asylum, but Spock subdues him with a Vulcan nerve pinch. In sickbay, the intruder identifies himself as Simon van Gelder, and a computer check reveals that he is not a patient, but Dr. Adams’ assistant.

When they inform Tantalus of van Gelder’s capture, Dr. Adams claims that van Gelder’s use of an experimental treatment device on himself is responsible for his disturbed condition. McCoy, suspicious, urges Kirk to investigate. Kirk transports down to the colony with one of the ship’s psychiatrists, Dr. Helen Noel.

Adams introduces them to a strangely emotionless staff member, Lethe, and gives Kirk and Noel a tour of the colony. Although he is affable and accommodating, his staff, like Lethe, all seem lacking in affect. Adams shows Kirk and Noel the treatment device he referred to: an experimental “neural neutraliser”. According to Adams, van Gelder tested the device on himself, with horrifying results. He further claims that the machine, harmless at low intensity, is used only to calm agitated inmates. Noel is satisfied with his explanation, but Kirk remains suspicious.

On the Enterprise van Gelder becomes increasingly frantic, warning that the landing party is in danger, but when he tries to explain the danger and refers to the neural neutraliser, he is convulsed with pain. Spock mind-melds with van Gelder, to enable him to tell his story. Spock learns that the neural neutraliser can empty a mind of thoughts, leaving only an unbearable feeling of loneliness, and that Adams has been using it on inmates and staff to gain total control of their minds. The first officer assembles a security team, but the colony’s force field blocks transport and communication.

Unaware of events on the ship, Kirk decides to test the neutraliser on himself, with Noel at the controls. She finds that she can easily implant thoughts into Kirk’s mind, even altering his memory of a recent Christmas-party encounter between the two of them. Adams then appears, overpowers Noel, seizes the controls, increases the neutraliser’s intensity, and proceeds to convince Kirk that he has been madly in love with Noel for years. Kirk and Noel are then confined to their quarters.

On Kirk’s orders, Noel enters the facility’s physical plant through a ventilation duct, and interrupts Kirk’s next neutraliser session by shutting off power to the entire complex. Freed from the neutraliser, Kirk attacks Adams, leaving him alone and unconscious in the treatment room. A guard discovers Noel’s sabotage, restoring power before turning his attention to her. She surprises him with a well aimed kick, propelling him into the circuitry and electrocuting him, and shuts off the power again. With the force field now off, Spock beams down to the planet, disables the force field, and restores power to the colony. This reactivates the neural neutraliser, which empties Adams’ mind completely, killing him.

Back on the Enterprise, Kirk is informed that van Gelder has destroyed the neural neutraliser. McCoy is surprised that loneliness could be lethal, but Kirk, after his experience, is not.

Star Trek TV Series

You can find a full index of Star Trek TV series here.

Star Trek TV Series, Films, and Documentaries

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Production & Filming Details

  • Director(s): Vincent McEveety.
  • Production: Desilu Productions (1966-1967) and Paramount Television (1968-1969).
  • Distributor(s): Paramount Pictures (1966-2006), CBS Paramount Television (2006-2007), and CBS Television Distribution (2007-Present).
  • Original Network: NBC.
  • Release Date: 03 November 1966.
  • Running Time: 50 minutes.
  • Country: US.
  • Language: English.

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