The detective understands that the encryption consists of the names of the criminals. Among the dangerous people, Holmes cites the example of Sebastian Moran - a retired colonel and respected man, but in reality a dangerous criminal. Holmes and Watson decide to track down the colonel, for which they visit the Bagatel club, in which Moran was a regular. At the club, Holmes receives a note requesting a meeting. The detective leaves, and Watson remains to observe Moran. Holmes is brought to Milverton’s mansion. In the office of the murdered man he is met by a tall, hunched man. This is Professor Moriarty - Napoleon of the underworld, head of a powerful criminal organization known throughout Europe; it was just Milverton and Moran. Moriarty guessed that Holmes was present in the house of the blackmailer during the murder, and the encryption was not taken by Scotland Yard, but Holmes, thereby disrupting the organization’s plans. Taking the moment, Holmes stuns the professor, picks up the taken revolver and leaves, saying that Moriarty has no evidence for him. While Holmes was talking with a professor, Watson witnessed an unpleasant scene at the Bagatelle club. The young aristocrat Ronald Adair, playing in tandem with Colonel Moran, accused him of cheating. But he, having silenced him, demands calmly sharing the winnings. In revenge, Adair, whose game was fair, returned the money to the losers. Returning home, Watson tells everything to Holmes. Holmes says that they both fell into the hands of a real criminal organization, and staying in London is not safe. Giving directions to Watson, Holmes escapes. The bandits set fire to the house, and Watson barely extinguishes it, sacrificing two carpets. The next day, Watson leaves, and, following Holmes’ instructions, gets into the right cab before the passage and, merged with the crowd, goes to the waiting crew, which was controlled by Mycroft. Along the way, the doctor meets Lestrade and asks him for the protection of Ronald Adair, mentioning the name of Sebastian Moran. With Holmes Watson meets already at the station, in a compartment. Holmes realizes that the Moriarty people have ambushed. Having traveled some distance, friends get off the train. They manage to move to the continent, to Switzerland. There they settle in a hotel run by Peter Steyler Jr. The owner joyfully greets them when he recognizes Holmes: the detective helped him avoid hard labor when Steiler stole Cupid’s head. In Switzerland, Holmes discovers that Moriarty’s gang has been captured, but with the exception of the leader himself. He and Watson go to visit one of the wonderful local attractions - Reichenbach Falls. The detective notes that this is a “well-chosen place” and feels doomed, while Dr. Watson, full of positive emotions, does not understand the complexity of the situation. A boy messenger runs to the waterfall and gives Watson a note asking the English doctor to examine the patient with consumption. The doctor is forced to retire. Holmes is left alone. He knew that Moriarty would crave revenge and simply killing Holmes was not enough for him. He came to Switzerland for Holmes and predicted the place of the match at the waterfall. When meeting with Professor Holmes asks him a few minutes to write the last letter, and he allows him. The detective leaves a note in a cigarette case near his outer clothing. A deadly duel began. Professor Moriarty perfectly mastered the baritsu fight and hoped to defeat Holmes soon, but he also had a good command of this fight. Returning to the hotel, Watson realized that the note was a distraction. Taking a revolver with him, he rushed back to the waterfall, and behind him - Peter with a gun. Meanwhile, the fight continued. Moriarty pulled Holmes to the edge of the cliff to die with him. When the outcome of the fight was close, Holmes discovered the shooter who appeared at the scene - Colonel Moran: he appeared when Watson left. Of the last forces clinging to Holmes, Moriarty slides off a cliff and dies in a waterfall, while Holmes remains hanging on the edge of the cliff in his arms. Moran shoots Holmes on the fingers, and he with a yell breaks off the cliff. Moran leaves. Watson comes running a little later and finds only the things of a friend. A shot rang out, but it was Peter who came to the rescue. Both of them mourn Holmes. Watson reads a suicide note in which Holmes says that he revealed the main business of his life, he also asks to take care of the unfortunate Ronald Adare.