As a British person, I absolutely adore Sherlock. This is one of the best episodes of them all, with the setting closer to the original books and set in Victorian England. The story tries to solve the mystery of how a bride who started shooting in the street, then shot herself, managed to then kill her husband later in the evening. The storyline is mirrored in modern times, and is incredibly complex so you have to be paying attention for the entirety of the episode. Finally leaving the audience on a cliffhanger as is usual in the series.