Season 2 ends with the relationship between Holmes and Watson coming to a crossroads, but they agree to put their differences aside to help Sherlock's brother Mycroft, who faces accusations of treason and murder.moreless
As Holmes and Watson work a standard murder investigation, they encounter MI-6 and find the case has international and political inferences. Watson re-examines her relationships with Mycroft and Sherlock.
The Lovejoy Antiques team is in Ireland looking for new stock (and also hoping to find a painting by Jack Butler Yeats, for Jane to give her uncle). A bungled robbery leaves them in possession of a page from a rare ancient book, and the search is on for an expert - Brendan Hennessey.