Guest Stars Rupert Graves as DI Lestrade Una Stubbs as Mrs. Hudson Mark Gatiss as Mycroft Holmes Andrew Scott as Jim Moriarty Chipo Chung as Presenter Sasha Behar as Dr Mortimer Stephen Wight as Fletcher Russell Tovey as Henry Knight Amelia Bullmore as Dr Stapleton Clive Mantle as Dr Frankland Will Sharpe as Corporal Lyons Rosalind Knight as Grace Gordon Kennedy as Gary Kevin Trainor as Billy Simon Paisley Day as Major Barrymore Sam Jones as Young Henry