The ransacking of Irene Adler's home

The episode begins with two burglars ransacking Irene Adler's house. Her coachman John catches the burglars in the act, and Irene follows into the room with a revolver in her hand. Without summoning the police, Irene motions the burglars to leave. John protests but she asks him to close the windows. In a voiceover, Dr. Watson explains that the beautiful Irene Adler of "dubious and questionable memory" has always been "The Woman" to Sherlock Holmes.

The letter and the visitor

Watson returns to Baker Street after several days away. As he enters, Mrs. Hudson tells him that Holmes has been "all on edge" and has instructed her not to bring him supper until she is called. Watson enters the drawing room to find Holmes sitting in an armchair staring into the fireplace. He sees a syringe in the half-open drawer of the table and thinks that Holmes has indulged in a dose of morphine or cocaine, but Holmes corrects him, saying that his true stimulant is a letter that received by the morning post.

The undated and unsigned letter states that a gentleman will arrive that evening to consult Holmes on a matter of importance. They deduce from the letter that the writer is a man and that the paper is of German origin. The grammar of the letter indicates that the writer is also German (".. only a German is so uncourteous to his verbs.."). Just when they have finished their deductions, they see a carriage pull up at their door. Holmes insists on Watson's staying in the room.

The masked visitor pushes past Mrs. Hudson and enters the drawing room. He introduces himself as Count Von Kramm, a Bohemian nobleman. After obtaining a promise from Holmes and Watson to maintain absolute secrecy for a period of two years, he says that the matter concerns the house of Ormstein, the hereditary kings of Bohemia. The visitor, who had confessed that the title that he has given is not his own, is surprised when Holmes says that he has already deduced both these facts and that the visitor is Wilhelm Gottsreich Sigismond von Ormstein, Grand Duke of Cassel-Felstein and the hereditary King of Bohemia.

The problem

The king explains that about 10 years ago during a visit to Warsaw, he came to know the adventuress Irene Adler. Holmes suggests that the king wants to recover compromising letters. Consulting Holmes' index reveals that Irene Adler was born in New Jersey in 1858, is a singer, has retired from the operatic stage, and now resides in London. When Holmes suggests several ways of questioning the authenticity of the letters, the king admits that she also has a photograph of both of them together.

He explains that all attempts to recover the photograph from Irene have failed, the location of the photograph is still unknown and she refuses to sell it. Holmes is impressed at Irene's cleverness and can't help laughing at the king's failed attempts. When Holmes asks about her intentions, the king tells him that she plans to ruin him. He is about to marry a young Scandinavian princess, and if the photograph becomes public, the marriage would be called off. After giving them money and both his and Irene's addresses, the king leaves.

Investigations at Briony Lodge

Holmes goes to Briony Lodge, Irene Adler's residence in London, in the disguise of an out-of-work groom and strikes up conversations with others in the mews. Later at Baker Street, Holmes tells Watson that he was able to find out about her daily schedule and that she has only one regular visitor, a lawyer named Godfrey Norton of the Inner Temple. The next day Holmes, again in disguise, is trimming the hedge at Briony Lodge and hears Irene singing. While he is listening, Godfrey Norton arrives in a cab and enters the house. Godfrey leaves soon afterwards, telling the cabbie to drive as fast as he can to the Church of St. Monica. Irene follows as well, and Holmes – telling the story to Watson – says that she has a "face a man might die for", language Watson finds quite surprising.

At the church, it turns out that Godfrey and Irene are getting married. Godfrey asks Holmes to be a witness, and after the ceremony, Irene gives Holmes a sovereign as a souvenir; both Godfrey and Irene go separate ways. Back at Baker Street, Holmes tells Watson that he will need his assistance that night in activities that may be against the law and may risk arrest, to which Watson readily agrees.

The drama at Briony Lodge

As Watson and Holmes, disguised as a clergyman, drive to Briony Lodge, Holmes tells Watson that Irene herself will show him where the photograph is kept, which Watson finds hard to believe. They leave the cab a little distance before Briony Lodge, in front of which an unusual number of people are gathered. When Irene arrives in her coach, two young men from the street rush to open the coach door, looking for a tip. A fight breaks out between the young men, and Holmes intervenes. One of the men strikes Holmes, who is apparently injured, and Irene asks that he be carried into her home.

Inside the house, Holmes says he feels faint, and Irene asks the maid to open the window. He asks for some smelling salts, and while Irene's back is turned, he motions to Watson, who is just outside the window and tosses in a plumber's smoke rocket. Holmes raises a cry of "Fire!" and in the ensuing confusion, Irene rushes to open a wall panel that reveals a button. Before she can press it she notices that Holmes is watching her. She immediately closes the panel, realizing that everything was a ruse to get her to reveal the hiding place. Holmes points out that the smoke is coming from the rocket and asks the coachman to tell the people outside on the street that it was a false alarm. With the hiding place now known, Holmes leaves in spite of Irene's inviting him to stay back for some refreshments.

Climax

As they drive back to Baker Street, Holmes tells Watson how Irene showed him the hiding place. He tells him that he plans on calling early the next morning as himself with the king and Watson to collect the photograph. As they are about to enter their home on Baker Street, a person walks past, saying "Good night, Mr. Sherlock Holmes."

The next day as they arrive at Briony Lodge, Holmes tells the king that Irene's marriage probably means she will not interfere with his plans. They find that she has already left England for the continent, never to return. Holmes presses the button in the panel to open a secret compartment that contains a different photograph of Adler alone and a letter addressed to him. In her letter Adler tells Holmes that she had been warned about him and that when she inadvertently revealed the hiding place, she realized that she had been tricked by Holmes. She had followed him, in a man's disguise, just to make sure, and greeted him good night at his door. She says that she had kept the photograph with her only to safeguard herself from the king and that she does not plan on using it against him anymore.

The king comments that Irene would have made a wonderful queen, and regrets "that she was not on my level." Holmes replies that "she is on a very different level to your majesty," implying that he regards her as superior. He apologizes that he failed to acquire the photograph, to which the king says that the photograph is now as good as if it was in the fire, since her word is inviolate. He offers Holmes his ring as a reward but Holmes asks for Adler's photograph instead and walks away without shaking the king's outstretched hand.