Doctor Who is a British science fiction television series that was produced by the BBC. According to the Guinness Book of World Records, Doctor Who is the longest running sci-fi television series in the world. The television series originally ran from 1963 to 1989 and a television film was produced in 1996.
The series went into production again in 2005 under the guidance of Russell T. Davies, with The Doctor being played by Christopher Eccleston for one series. Eccleston was succeeded by David Tennant, the tenth Doctor, who played the role for three series. Doctor Who: The Waters of Mars is the second of four specials that comprised series four and finished up Tennant's tenure on the show. He'll be replaced by Matt Smith in the fifth series, which will air in 2010.
The Doctor is a Time Lord, a member of an extraterrestrial race that can travel through time. He uses his abilities to explore the universe and avert any disasters he encounters. He travels through time in a blue police box (remember, this is a British series) called the TARDIS. In Doctor Who: The Waters of Mars, The Doctor lands on the planet Mars near an outpost called Bowie Base in 2059. He meets Dr. Adelaide Brooks, the captain of Mars' Bowie Base, played by Lindsay Duncan (Alice in Wonderland, 2010). The base's members are all amazed to find another human on Mars and cannot figure out where he came from. The Doctor lets slip that he knows who all of the members of the base are and rattles off their names and rank. This makes them even more suspicious and interested in knowing who he is and how he knows them and makes the viewer aware that something pivotal is going to happen that involves Bowie Base.