Sister Lamont

Sister Lamont was a nurse at an oil rig infirmary. She was abducted by the Zygons and her body-prints used by Odda. The Fourth Doctor found the real Lamont in the Zygon ship, along with the other abducted humans, and helped them escape prior to setting the ship to self-destruct.

Biography from the TARDIS Data Core article, licensed under CC-BY-SA