Guest Stars Rupert Graves as DI Lestrade Una Stubbs as Mrs. Hudson Louise Brealey as Molly Hooper Mark Gatiss as Mycroft Holmes Amanda Abbington as Mary Morstan Siân Brooke as Eurus Holmes Lindsay Duncan as Lady Alicia Smallwood Tom Brooke as Bill Wiggins Toby Jones as Culverton Smith Gina Bramhill as Faith Katy Wix as Nurse Cornish Georgina Rylance as Carmelia Eric Koflabrefa as Policeman Martin Savage as Ivan Matthew Romain as Nervous Andrew Usman Akram as MI5 Agent David Kirkbridge as Policeman Sharon Ballard as Policewoman Asheq Akhtar as Sahaad Lee Knight as Reporter Vijay Doshi as Gavin Ben Abell as Indignant Man Miranda Hennessy as Reporter Dominic Borelli as Husband Eileen Dunwoodie as Wife