Holmes and Watson come into contact with MI-6, the British intelligence agency, when a standard murder investigation turns out to have international and political implications. Meanwhile, in the wake of a crisis, Watson reevaluates her relationships with Sherlock and his brother, Mycroft.
Elenco: Jonny Lee Miller , Lucy Liu , Jon Michael Hill , Aidan Quinn , John Noble , Natalie Dormer , Ophelia Lovibond , Rhys Ifans , Sean Pertwee .