Sebastian was a tour guide for new arrivals visiting the Edge. He told the Second Doctor that the Edge was a place where the cutting edge of academic research was going on. He explained that the Asteroid on which the facility was located was fragile, and if some parts broke off, then it would completely collapse. When the Doctor asked to have a tour of the labs, he had to give him a test to do it. He was helping to sell a mind-enhancing drug, Acuman. He was later ordered to kill Jamie McCrimmon by Provost Curtis. (AUDIO: The Edge)

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