Guest Stars Rupert Graves as DI Lestrade Una Stubbs as Mrs. Hudson Mark Gatiss as Mycroft Holmes Andrew Scott as Jim Moriarty Amelia Bullmore as Dr Stapleton Sasha Behar as Dr Mortimer Russell Tovey as Henry Knight Clive Mantle as Dr Frankland Chipo Chung as Presenter Stephen Wight as Fletcher 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
