The respected penologist who ran the Tantalus V colony and secretly used the neural neutraliser to control the minds of others.
Tristan Adams is the director of the penal colony on Tantalus V, widely admired for his supposedly enlightened methods of rehabilitation. When his escaped assistant Simon van Gelder reaches the Enterprise, Adams claims that van Gelder was injured in an accident involving a new treatment device.
Kirk and the psychiatrist Helen Noel discover that Adams has been using the neural neutraliser to erase and rewrite thoughts. He uses it on Kirk, but Noel cuts the colony's power, and Adams is later found dead in the neutraliser chamber, his own mind emptied by the machine. He was played by James Gregory.