Constantine (The Empty Child)

Dr Constantine was the last person in Albion Hospital to be affected by the gas-mask virus created by the Chula nanogenes, he was able to show the Doctor that the seemingly dead patients were just immobile until triggered by something. Like the four-year-old boy they were now based upon, the only question in their minds was "Are you my mummy?" Constantine had done some experimental therapy with the 'empty' child in Room 802 and recorded it - his empathy existing perhaps due to the fact he had lost his own children and grandchildren to the war. Eventually Constantine succumbed and became a gas mask zombie like the others, threatening the Doctor, Rose Tyler and Captain Jack Harkness. When the nanogenes later recognised the correct human DNA, they repaired all those who had been infected, restoring Constantine, who was then able to carry on his good work at the hospital. (DW: The Empty Child/The Doctor Dances)