Lady Marie Ernhardt was the wife of Lord Ernhardt in Klimtenburg during the 19th century. After suffering radiation poisoning from a crashed Cyber-ship, she died. However, unbeknownst to her husband, her body was recreated by the Watchman using cybernetics scavenged from the same ship. In consequence, she gained inhuman strength and immortality.
When the Cybermen started an attack on the village, she assisted the Eleventh Doctor and Olga Bordmann in stopping them from recharging their energy.Her son sacrificed himself to destroy the Cybermen in the process, who had been augmented with a cyber body just like herself. During the battle, Marie sacrificed herself to buy the Doctor time, but was later rebuilt by him and reunited with her husband. (PROSE: Plague of the Cybermen)