context: Doctor Who is a British science-fiction television programme produced by the BBC since 1963. The programme depicts the adventures of the Doctor, a Time Lord—a space and time-travelling humanoid alien. He explores the universe in his TARDIS, a sentient time-travelling space ship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Accompanied by companions, the Doctor combats a variety of foes, while working to save civilisations and help people in need.
question: What is the alien's mission?