Driscoll was a member of an armed radiation team sent to get Sarah Jane Smith out of the reactor room. When the team couldn't get through the doors, the Fourth Doctor found a way in through a cooling duct. After Sarah was removed from the fusion room, Driscoll returned to remove Eldrad's hand for examination and containment. He found Eldrad's ring at the same time and it brought him under the Kastrian's influence.
The Doctor noticed that the ring was missing and Sarah, barely able to remember anything, didn't know anything about it either. Driscoll volunteered to go back in and search for it. He returned, and claimed he had found nothing.
In decontamination, he knocked Elgin unconscious, took Eldrad's hand and headed for the reactor core. When the Doctor realised that he must have been taken over, he set out in pursuit of him and told others to stop him as well. They were unsuccessful. Driscoll used the power of the ring to incapacitate the guards sent after him. Entering the reactor room, he unlocked the door to the core and went in with the hand. He was vaporised and Eldrad absorbed the radiation, regaining humanoid form. (TV: The Hand of Fear)