Starting around 2246, Adams began work that revolutionized prisons and the treatment of prisoners. His theories transformed prisons from cages into clean, decent hospitals for sick minds. Captain James T. Kirk believed Adams' work had done more than the rest of Humanity had done in the previous forty centuries. This auspicious beginning made Adams' tenure at the Tantalus Penal Colony and subsequent death baffling to those who knew him.
In early 2266, Dr. Simon Van Gelder joined Dr. Adams as an associate. Six months later, Van Gelder was severely ill, barely able to remember his own name. When the USS Enterprise visited the colony for routine resupply, Van Gelder managed to escape. Dr. Adams provided an explanation for Van Gelder's illness, but Dr. McCoy doubted Adams' account. Regulations required Kirk to investigate; he visited the colony, along with Dr. Helen Noel, to meet with Adams and learn what had happened to Van Gelder.
Spock and McCoy eventually learned that Van Gelder had been injured by Adams himself, who was conducting unauthorized and unethical experiments on all the patients and staff, turning them – with the exception of Van Gelder – into mindless zombies. By the time they learned this, Adams had imprisoned Kirk and Noel, and was subjecting Kirk to the neural neutralizer, with the declared goal of learning more about this form of therapy.
Noel, acting on Kirk's instructions, managed to briefly shut off the power to the facility as part of an escape attempt. During a scuffle that followed, Adams was left stunned on the floor of the neural neutralizer treatment room, and Kirk escaped. When Spock restored power a few moments later, he also unwittingly restored power to the neural neutralizer. Adams was still in the room and was subjected to unsupervised exposure to the beam for an extended period. This exposure emptied his mind, killing him. (TOS: "Dagger of the Mind")
Tristan Adams was portrayed by James Gregory.
In Shimon Wincelberg's original script of "Dagger of the Mind", the character was called "Doctor Asgard", his name being a reference to the gods' living place in Norse mythology. The "Tristram Asgard" was what was noted in the de Forest Research document dated 26 July 1966.
In the final draft script of "Dagger of the Mind", Adams was initially described thus; "Mid-forties, hardly the stereotype of a famed scientist, he has broad, warm features, a suspicion of old freckles at the nose, and aggressively friendly manner which promises firm handshakes, humor, an ounce of brandy at the right hour and complete candor at all times [....] A man interested in many things, artistic, comfortable, masculine interests as well as scientific."
Whereas Adams is canonically implied as having invented the neural neutralizer, he was outrightly stated to have created the device in the final draft script of "Dagger of the Mind". Various script drafts revealed his reason for constructing the neural neutralizer and conducting experiments on innocent people as being dissatisfied with Humanity and doing good for others without being properly redeemed for it, and deciding on gaining the only thing he was still interested in, in life: power. He was also skeptical that, without the device, Humanity would give him what he ultimately wanted and believed he deserved, such as "a very comfortable old age." Adams referred to himself as "a most selective man" who didn't have much else except his reputation and, due to the neural neutralizer, power, but also too much knowledge about "men's minds" to be as optimistic as Kirk. However, Gene Roddenberry removed these lines from the revised final draft script of "Dagger of the Mind", suggesting that Humanity had overcome such petty differences and hateful emotions in the future. Hence, Adams' motivation for his actions was never explained. (These Are the Voyages: TOS Season One)
Dr. Tristan Adams' name was mentioned on a Planet 10 Shipping label, which is visible in DS9: "A Simple Investigation" (though with the small print, including his name, blurred) and in the Star Trek Encyclopedia (3rd ed., p. 448).