Written by: Jamie Mathieson and Steven Moffat Directed by: Ed Bazalgette Guest starring: Tom Stourton, Ariyon Bakare, Simon Lipkin, Ian Conningham, Murray McArthur, Barnaby Kay, John Voce and Struan Rodger Ooh, look. It's TV's very own Maisie Williams in an undisclosed role that looks set to "challenge the Doctor in mysterious ways". Whatever that means. The popular Game of Thrones star will be guest starring in Episodes 5 and 6 as an enigmatic character who could be "good or bad", according to the actress herself. Let's face it, though, she's probably just another incarnation of River Song. Or not. These two period adventures (that's 5 and 6) form a "linked story" rather than a traditional two-parter, and they've both been directed by Ed Bazalgette whose most recent work includes the BBC One drama Poldark. This episode, intriguingly titled The Girl Who Died, has been co-written by Jamie Mathieson who contributed two of the most popular episodes last year, Mummy on the Orient Express and Flatline, so fans have high hopes indeed.