The plot of this episode was inspired by the Holmes short story, "The Adventure of the Bruce-Partington Plans."
According to the DVD commentary, this was the first episode to be produced after the BBC accepted the series. The series was filmed in reverse order because Steven Moffat, the writer of the first episode A Study in Pink (2010), was busy with the fifth series of Doctor Who (2005).
According to the episode commentary, the smiley face on the wall of 221B Baker street is painted by the same light yellow paint used by the Black Lotus Tong in The Blind Banker (2010).
According to the episode commentary, The voice of the little boy is provided by Louis Oliver, son of Steven Moffat and producer Sue Vertue, who played little Sherlock on the later episodes.
According to the episode commentary, the photos of a young Carl Powers on the wall of 221B are actually childhood pictures of the show's Second Assistant.