You know how last week I said I was looking forward to how the Twelfth Doctor was going to act in an episode that didn't feature Clara Oswald at his side? Well it seems I might have jumped the gun a bit on that assessment, as Mummy on the Orient Express picks up some weeks after the events of last week's Kill the Moon . Written by another Doctor Who first time writer Jamie Mathieson , this episode places the duo on a rather silly but appropriate setting for a good old fashioned murder mystery adventure.