The Star Trek episode "Dagger of the Mind" aired on November 11, 1966, and is set in the 23rd Century on the U.S.S. Enterprise. Captain Kirk (William Shatner), Spock (Leonard Nimoy), Dr. McCoy (DeForest Kelley), Scotty (James Doohan), Sulu (George Takei), Checkov (Walter Koenig), and Uhura (Nichelle Nichols) all appear in this episode.

The episode focuses on the Enterprise crew's actions after receiving a distress call from the Tantalus Penal Colony. There, they find that the colony director, Dr. Tristan Adams (Malcolm Muggeridge), uses a device called the "Neurosomatic Integration Replicator" to conduct mind control experiments on the inmates.

The Enterprise crew soon discovers that Dr. Adams has been using this device to control the mind of Helen Noel (Marianna Hill), a female psychiatrist and former classmate of Kirk's. Kirk and Spock work to break the mind control and learn the truth behind the experiments. Meanwhile, the female characters of Uhura, Noel, and Yeoman Barrows (Barbara Baldavin) show firm resolve and courage, re-establishing all critical systems that have faltered in the face of danger.

The episode culminates in a fight between Kirk and one of Dr. Adams' henchmen, after which the mind-control device is destroyed. The crew then manages to escape from the penal colony and return to the Enterprise.

After appearing on Star Trek, Marianna Hill went on to appear in films like "Escape from the Planet of the Apes" (1971), "The Stepford Wives" (1975), and "The Dark Secret of Harvest Home" (1978). In addition, she guest starred in various television series, including "Kojak," "Police Story," and "The Six Million Dollar Man."

Interesting facts about the filming of this episode include that William Shatner and Marianna Hill had previously worked together on an episode of The Virginian (1962). In addition, this episode of Star Trek was the first in which the Vulcan nerve pinch was used, which has become iconic in Star Trek lore.