[[caption-width-right:320:Spock and Van Gelder share the very first MindMeld.]]

The ''Enterprise'' is delivering some huge ass bottles of drugs to the Tantalus PenalColony. (Wonder where they got big enough cotton balls?) They also pick up a box marked "Do Not Open" and addressed to "Bureau of Penology, Stockholm, Eurasia-NE". Not sure what it was supposed to be holding, but it is soon revealed to be holding a crazy old man who knows karate!

The crazy old man is at first believed to be an escaped inmate from Tantalus, but it's discovered that he's actually Simon Van Gelder, one of the doctors. Dr. Adams tells Kirk that Dr. Van Gelder pulled a ProfessorGuineaPig while working on a device called the Neural Neutralizer, losing his mind in the process. And would he kindly return him? Bones tells Kirk he smells a rat. Kirk gives Adams some B.S. about how they can't due to some red tape. Adams good naturedly accepts this and cordially invites Kirk down for a visit. Kirk takes him up on this. Bones suggests Kirk take a psychological expert with him. He recommends Dr. Noel. It seems Kirk and Dr. ''Helen'' Noel have met before. Apparently, even in the future office Christmas parties can get out of hand...

This episode is also known as "The One That Got [[Recap/SouthParkS2E11RogerEbertShouldLayOffTheFattyFoods Parodied Off]] By ''WesternAnimation/SouthPark''".

!!Tropes for this episode include:

* AboveTheInfluence: Dr. Helen Noel flirts with Kirk, but he refuses to reciprocate. Later on, Kirk is {{Brainwashed}} into thinking he's in love with her and she desperately tries to explain what happened, in fact seeming rather creeped out.
* AbsenteeActor: Scotty and Sulu are absent from this episode.
* AffablyEvil: Adams seems so charming and polite at first. [[WineIsClassy He makes a toast]] [[ThePowerOfLove to "love and warmth"]], but it's only a MaskOfSanity.
* AgonyBeam: There's a MindRape machine that looks like a sun lamp shining on a hair-salon chair. And Kirk isn't even strapped in. He '''could''' just stand up and walk off, but apparently it's so intense that he only sit there writhing in pain as a sort of post-hypnotic suggestion is used on him.
* AirVentPassageway: How Dr. Noel makes her escape to find the circuit breaker that will turn off the neuralizer.
* ArcSymbol: The logo on Dr. Adams' boiler suit and that of his "helpers" is a hand freeing (or crushing?) a dove under a stylized sun. Or is that "sun" actually the round, flashy light of the Neural Neutralizer?
* BigDamnKiss: Kirk plants one on Noel. She reluctantly tells him that he was only hypnotized to think he was in love with her.
* BigNo: When Dr. Van Gelder tries to warn Kirk against staying on Tantalus.
* BridalCarry: Noel induces an ImagineSpot for Kirk suggesting that he carried her into his quarters this way. It was to remind Kirk of their one night stand after a prior Christmas Party.
* BrokenAce: Van Gelder. Perhaps Adams to a degree.
* CantArgueWithElves: Spock finds it interesting that "Your Earth people glorify organized violence for forty centuries, but you imprison those who employ it privately." Even Bones has no come back for that.
* CreepyMonotone: Lethe. "I love my work."
* EarlyInstallmentWeirdness: For some reason, Kirk tells ''Spock,'' who appears to be at the science station, to "take us out of here, warp factor one."
* EmotionsVsStoicism: Spock says "Where there is no emotion, there is no motive for violence."
* EmptyShell: Adams uses the Neural Neutralizer to render people into mindless servants.
* {{Expy}}: The Neural Neutralizer works a lot like the Ludovico Treatment from ''Literature/AClockworkOrange''.
* FreakOut: Dr. Van Gelder has the mother of them all. Screaming, raving, crazy eyes, violent outbursts. He shouts "I am not a criminal!" Incidentally, the actor needed a four day reprieve after this emotionally taxing role.
* GildedCage: Kirk points out to Bones that modern mental institutions may as well be vacation resorts. Bones replies "A cage is a cage, Jim."
* GirlOfTheWeek: Dr. Helen Noel.
* GoMadFromTheIsolation: The fate of Dr. Adams. The complete lack of any mental stimulation at all made his brain shut completely down.
* HeroicWillpower: Kirk apparently has this or something similar, judging by Adams' comment about the strength used on him without effect having broken down Van Gelder.
* HoistByHisOwnPetard[=/=]KarmicDeath: Adams dies by having his mind completely wiped by the same machine that he used on Van Gelder and Kirk.
* LiteraryAllusionTitle: From ''Theatre/{{Macbeth}}'': "Or art thou but A dagger of the mind, a false creation Proceeding from the heat-oppressed brain?"
* MadDoctor: Dr. Tristan Adams went a little too [[BrainwashedAndCrazy happy]] with his machine for rehabilitating mental patients.
* MeaningfulName: Lethe is the name of the river of forgetfulness in Greek myth. Tantalus was sent to Tartarus for murdering his son and punished by being never allowed to eat or drink. And isn't it funny that the girl Kirk met at a Christmas party was named "Noel"?
* MentalFusion: Spock Mind Melds Van Gelder to pick info from his troubled mind.
* MindControlDevice: A "hospital" basically zombifies people with a hypno-spinny-thingy. Trying to remember what happened to you, let alone tell others, causes increasing pain and eventually death.
* MoreHypnotizableThanHeThinks: Had Kirk try out the Neural Neutralizer, complete with him not realizing he blanked out for a second when it was turned on.
* MuggedForDisguise: Dr. Van Gelder knocks out a RedShirt and steals his jumpsuit in attempt to fit in. It only works for awhile.
* PantyShot: [[HelloNurse Hello]], Dr. Noel!
* PlotHole: Dr. Helen Noel is one of the Enteprise's psychiatrist'''s'''. So, why Bones isn't assisted by any of them for the puzzling case of Van Gelder?
* PressurePoint: Dr. Van Gelder is felled by Spock applying the Vulcan neck pinch.
* PsychoPsychologist: Dr. Tristan Adams
* RedShirts: They get off easy in this ep. Two get karate chopped, one gets put in a chokehold until he passes out. It's possible that Dr. Van Gelder wasn't far gone enough to murder and just knocked them out for awhile.
* ShoutOutToShakespeare: The title comes from the soliloquy of ''Theatre/{{Macbeth}}'' ("A dagger of the mind, a false creation").
* SilentSnarker: The [[http://tos.trekcore.com/hd/albums/1x09hd/daggerofthemindhd229.jpg face Spock makes]] when Noel and Kirk say hello and he realizes he's meeting yet another of his Captain's exes. Which is nothing to his reaction when he bursts into the asylum, phaser at the ready, only to find Kirk planting a kiss on her ([[{{Brainwashed}} although that last wasn't exactly Kirk's fault]]).
* TeleportInterdiction: The Tantalus penal colony has a security force field which must be deactivated to allow beaming up or down. The RedShirt gets teased for forgetting that.
* WoundedGazelleGambit: After being pulled away from the high-voltage power control, Noel mimes the classic "swooning damsel" pose. When the orderly moves to apprehend her, she kicks him into the live wires with both feet.
* TheXOfY: The "Dagger of the Mind".