Margaret Cain

Margaret "Maggie" Cain was a member of the Bowie Base One crew.

Biography
Born in Grenoside, Sheffield on 28 December 2028, she graduated from the University of Sheffield with a first-class honours degree in chemistry. Her first job was as an engineer for a division of the GEC in London, where she also began studying part time for a PhD at Birbeck College. She was a British cosmonaut on the Russian Federal Space Agency mission Project Midas, beating over twenty-five thousand other candidates. In 2051, Margret became the second British woman to walk on the moon. She met the first, Adelaide Brooke, and the two developed mutual respect. Consequently, Brooke asked Cain to join the Bowie Base One mission.

She arrived at the base in 2058 and worked there, studying the planet Mars. She was attacked by Andy Stone after he was infected with the Flood virus. Maggie fell unconscious and was found by Tarak Ital, Brooke and the Tenth Doctor. She awakens as they walk down the biodome, unwittingly carrying the mysterious virus which is hiding in her body, but she has amnesia of the previous occurrences. After being placed in sickbay, she tries to get Yuri to open the door for her to come out, but Yuri refuses, saying a little rest won't hurt. In in a conversation with Yuri, Maggie's virus finally becomes active. The organism occupying her body reveals its desire to reach Earth, a planet rich in water. Yuri is first alerted to her transformation when she speaks in a deep voice distorted by the internal fission, "We should like that world", while gazing at planet Earth on a monitor, and Yuri, stammering in horror, briefly describes what has happened to their comrade: the skin around her mouth has become horrifically cracked and broken, her teeth have blackened and she is emitting water in an overwhelming torrent from her mouth, as if she is drowning.

In the medical dome, the Doctor and Adelaide meet the infected Maggie, who just stares at them all, but she suddenly takes an interest in the Doctor when he speaks ancient North Martian to her, Maggie appearing to understand it. Yuri evacuates the Medical Dome and heads for the Central. After he leaves, Maggie breaks out of confinement by seeping water into the door and alerts Andy and Tarak in the biodome corridor to the humans' plans by emitting a terrifying alien scream that is heard by the two men over a hundred metres away. The infected men slowly lower their heads and then look towards the medical dome from which the scream is coming from, then they slowly walk away.

With the other infected members, she tried to infect the remaining crew and escape to Earth. Maggie infects Ed Gold, who blows up the ship before his transformation, killing himself and stranding the Flood on Mars. After Steffi and Roman were infected by the Flood, the infected personnel all arrive at the glacier and attempt to crack the ice. Maggie and the other infected personnel were killed when Adelaide blew up the entire base. (TV: The Waters of Mars)

Behind the scenes

 * The Doctor's flashback to Maggie's obituary notes that she was from Grenoside, Sheffield, and was a chemistry graduate from the University of Sheffield, two things she shared with, the first Briton in space.
 * Like the other female member of the Flood, Steffi Ehrlich, she kept her eye colour. It seems the males had milky, blue eyes while females kept their colour. The Doctor noted this during the episode and suggested that it meant she was closer to human than the others.