: The Minister has lost an important letter. Sherlock Holmes discovers that the letter was stolen by the wife of the minister, who was blackmailed by a former lover, a well-known spy, and returns the document without giving out the woman.

Trelawney Hope, Minister for European Affairs, seeks help from the great detective Sherlock Holmes. He arrives at an apartment on Baker Street, accompanied by the Prime Minister. A few days ago, Mr. Hope received a letter from a foreign monarch of important national importance. In the afternoon, he kept it in the safe of the ministry, and at night brought it home and put it in the bedroom, in a box with secret documents. In the morning, the letter disappeared.

No one knew about the existence of the letter, and no one could get into the bedroom either. Wife Hope only announced the letter after his disappearance. Two or three people knew about the letter in the government, and only the one who wrote it abroad. If the letter is published, then the country may be drawn into the war.

No stranger could get into the bedroom, therefore, the letter was stolen by someone from home. A thief could pass it on to one of the international spies. There are three such people. You need to find out what they are doing at the moment.

After the visitors leave, Dr. Watson opens the newspaper and sees a note stating that one of the suspects, spy Eduard Lucas, was killed with a knife at home. The murder was not committed with the purpose of robbery, since valuables were not stolen.

While the great detective is considering whether there is a connection between the murder and the abduction of an important document, an excited Mrs. Hope comes to him. She knows that her husband was here, he is in trouble, she is worried about him and wants to find out what is the matter. Holmes cannot give Mrs. Hope any explanation. He is worried that the woman tried to sit with her back to the light and hide her face, but women are hard to understand. Maybe she was worried about the lack of face powder or poorly curled hair?

It takes three days. The great detective receives information from the government every hour, but the international situation is still calm. Accompanied by Watson and police inspector Leystred, he comes to the house of the murdered. Leystred says that the identity of the killer of Lucas is established. This is his secret wife, a Frenchwoman who suffers from a mental breakdown. Most likely, the murder was committed due to jealousy.

During the investigation, a constable was assigned to the house, which ensured that all things in the house remained in their places. When the investigation was completed, the police decided to put the room in order and found that someone was touching the carpet lying on the floor. The blood stains on the carpet and on the floor do not match. The great detective sends Leystred to talk with the constable in private and find out who raised the carpet, and meanwhile he feels the parquet under it. Finally he finds a cache that turns out to be empty.

The constable admits that a young woman mistakenly entered the house last night. Out of boredom, the constable decided to chat with a lovely stranger and told her about the murder.The woman became interested and asked permission to look at the crime scene. Seeing the blood, she fainted. While the constable was running after the cognac, she had already left.

Holmes, accompanied by Dr. Watson, comes to visit Mrs. Hope. He demands that she give him a letter, promising to settle everything. Realizing that her secret was revealed, a woman on her knees begs the great detective to help her. Once, as a young inexperienced girl, she wrote her lover Edward Lucas an imprudent letter. Years passed, suddenly Lucas showed up and began to threaten that he would show a letter to her husband. In exchange for the letter, Mrs. Hope was to hand over the document.

Unaware of the consequences of the disappearance of the letter, she stole it and brought it home to Lucas. Lucas put a document in her hiding place and gave the promised letter. Suddenly a woman with a dagger burst into the house and attacked Lucas, screaming that she had finally found him with her mistress. Mrs. Hope ran away in horror, but a new misfortune awaited her at home: the loss of a document could ruin her husband's career. By cunning, she took a document from the cache, and now does not know how to return the letter without telling her husband the truth.

Holmes opens the box and puts the letter between the sheets of some document and advises Mr. Hope to take a closer look at the box, as most likely the letter did not disappear anywhere, otherwise it would have been published a long time ago. In front of the Prime Minister, the amazed Mr. Hope finds a letter and runs to please his wife.

It seems strange to the Prime Minister that the document did not disappear, but the great detective has his own diplomatic secrets.