Military Intelligence Service Director Mycroft orders Albert to recover classified papers that could rock the nation, and kill the woman who stole them. Sherlock is hired by the king of Bohemia to pursue Irene Adler, who threatens the king’s wedding plans.

A culprit is arrested in the Jack the Ripper case which was solved by the Moriartys. Suspecting a frame-up by Arterton, Lestrade asks Sherlock for help in finding evidence that would prove it. Meanwhile, Paterson works to sneak Bonde inside the station.

Milverton blackmails Mary, exploiting her dalliance in antigovernment activities as a student. Sherlock decides to sneak into Milverton's estate to steal his evidence, but even that act was anticipated. Sherlock finds that he is not the only trespasser.