Terror of the Zygons - Part Two
The Doctor rushes to the infirmary but Sarah and Harry have disappeared. The Doctor asks Sister Lamont, the nurse, but she didn't see them leave. The Doctor finds Sarah in a decompression chamber, passed out. Someone locks them both in the decompression chamber while he is trying to revive her. The Doctor puts Sarah in a deep trance to keep her from freaking out. He then places himself in a deep trance and stays like that until Sgt Benton finds them and frees them.
The Zygons take Harry to their base/space ship. They explain a little bit about why they are on Earth and what their plans are before they take him to the body print room and demonstrate how they can use body prints of humans to take on human appearance.