In 2266, he was assigned to the Tantalus Penal Colony as Dr. Tristan Adams' associate. He was later promoted to director. By the time the USS Enterprise visited, six months later, he was suffering from the effects of neuro-synapse damage. Van Gelder's revelations prepared Spock to act, so that when Dr. Noel temporarily interrupted the power, Enterprise personnel were able to secure the colony. Dr. Van Gelder was restored to health, and resumed his responsibilities. He also dismantled the neural neutralizer room and destroyed the equipment. (TOS: "Dagger of the Mind" )