Website Hollywood.comhas been speaking to Steven Moffat about the upcoming series and the mystery of new companion Clara (played by Jenna-Louise Coleman). The current showrunner said:
"She's the insolvable mystery and the enigma, and he's the one chasing
after her. The Doctor wants to
solve the mystery of Clara. You will uncover the mystery of Clara in the next eight episodes. All will be made clear. You'll get your answer."
