BBC Programme Information have released a brief summary of episode one of the third series:
“David Tennant returns to his role as the Doctor and meets his brand-new companion in the highly anticipated third series of Russell T Davies’s Doctor Who.
For Martha Jones, a medical student in Central London, an ordinary day turns into a nightmare when her entire hospital is transported to the Moon.
There, she has to battle the Judoon and outwit a blood-sucking Plasmavore � but can she trust a mysterious stranger called the Doctor?
David Tennant plays the Doctor and Freema Agyeman plays his new assistant, Martha Jones. Russell T Davies is also the executive producer.”