Plot summary
Sherlock is commissioned by Mycroft to investigate the suspicious death of a government employee, who was working on a top-secret defence project: the Bruce-Partington Project. After rejecting the case and handing it over to John, Sherlock begins to be taunted by a criminal who puts his victims into explosive vests and sets Sherlock deadlines to solve the apparently unrelated cases, which include a twenty-year-old cold case involving the shoes of a drowned boy, the disappearance of a businessman, the death of a TV personality, and the assassination of a museum security guard by the " Golem ".
As Sherlock solves the cases, he finds links between them. After clearing up the original case regarding the government employee, Sherlock tries to force his unseen adversary to reveal himself. Near the end of the episode, Sherlock and "Jim Moriarty" (Andrew Scott) reach a standoff, where Jim reveals that he is responsible for the crimes. In the final seconds, Sherlock Holmes points his gun at a bomb on the floor that had been strapped to John. The episode's storyline is somewhat derived from " The Adventure of the Bruce-Partington Plans " and makes references to " The Five Orange Pips " at various points (as per the five bomb victims and electronic beeps on the phone) in addition to other works of Sir Arthur Conan Doyle.
Credits
Adapted from Wikipedia contributors, List of Sherlock episodes. HTML formatting and reference markers removed.