First Scientist

The First Scientist and another Sensorite scientist worked to cure John of the madness caused by the Sensorites' telepathic attacks on his mind. He was recognized by his wearing of a type of medallion. He and the other scientist later helped the First Doctor test the water on the Sense Sphere for poison, specifically atropine. When they found the poison, they helped the Doctor to develop an antidote.

He showed the Doctor to their aqueduct, and later showed Ian Chesterton and Susan Foreman the way to the aqueduct to rescue the Doctor. When the Doctor, Ian and Susan returned from the aqueduct, the scientist showed them the various items left behind by the humans that had visited the Sense-Sphere ten years previously. (TV: The Sensorites)