Synopsis
The empty house across from Baker St flat has a clear view of a wax Holmes, which is bait for Colonel Sebastian Moran, a surviving lieutenant of Moriarty. In April 1894, Watson (now a widower) checks 427 Park Lane where a young gambler, the Honorable Ronald Adair, was shot in a closed room on the 30th of March. He bumps into a wizened old book collector, who follows him home to his Kensington practice study then drops his disguise - it is Holmes.
Holmes apologizes for the deception needed to outwit his enemies, and describes his three years' exploits. He needed funds, so he confided in his brother Mycroft, who had preserved Sherlock Holmes' rooms. After a roundabout route, they wait two hours until around midnight in the abandoned Camden House, when Moran fires a specialized air-gun, fooled by Mrs Hudson moving the effigy from below to simulate life. Watson knocks down the villain, while Holmes whistles for Inspector Lestrade and the police.
Back at Baker Street, Holmes explains. Adair threatened to expose card-partner Moran whom he found cheating, and had locked himself in to count out the spoils he wanted to return.
Read more about this topic: The Adventure Of The Empty House