Dagger of the Mind

At Tantalus V, a rehabilitation colony for the criminally insane, the inmates have taken over the asylum using a neural neutralizer, which is used to remove (or implant) memories from a subject's mind. One colony administrator, Simon van Gelder, escapes to the Enterprise, leading Captain Kirk to investigate the colony. While on the surface, Kirk is brainwashed and taken prisoner, but is helped by Dr. Helen Noel, a colleague from the Enterprise who joined him on the planet. Spock performs a mind-meld with van Gelder to counteract the effects of the neutralizer, healing his mind and allowing van Gelder to take over the colony after Kirk and Noel's rescue.[37]