Guest Stars Una Stubbs as Mrs. Hudson Rupert Graves as DI Lestrade 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 Katy Wix as Nurse Cornish Toby Jones as Culverton Smith Gina Bramhill as Faith Georgina Rylance as Carmelia Miranda Hennessy as Reporter 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 Eric Koflabrefa as Policeman Vijay Doshi as Gavin Ben Abell as Indignant Man Dominic Borelli as Husband Eileen Dunwoodie as Wife