Doctor Who: The Crowmarsh Experiment

When attacked on an alien world, Leela falls unconscious... only to wake in another time, another place. She is in the Crowmarsh Institute on Earth, in London, in 1978, and everyone is calling her Doctor Marshall. They tell her the world she has known is but a fantasy, a delusion, and that this place is the one that is real. Surrounded by familiar faces on unfamiliar people, Leela knows what is true and what is false. But how long can she believe when everyone around her says it's a dream? What's really happening here?