Benedict Cumberbatch Sherlock Actor Martin Freeman Watson Actor Rupert Graves DI Lestrade Actor Una Stubbs Mrs. Hudson Actor Louise Brealey Molly Hooper Actor Russell Tovey Henry Knight Guest Star Amelia Bullmore Dr Stapleton Guest Star Clive Mantle Dr Bob Frankland Guest Star Simon Paisley Day Major Barrymore Guest Star Sasha Behar Dr Louise Mortimer Guest Star Will Sharpe Corporal Lyons Guest Star Stephen Wright Fletcher Guest Star Gordon Kennedy Gary Guest Star Kevin Trainor Billy Guest Star Rosalind Knight Grace Guest Star Chipo Chung Presenter Guest Star Paul McGuigan Director Steven Moffat Writer Mark Gatiss Writer, Executive Producer Beryl Vertue Executive Producer