In this story, we are in one wretched November night, and Inspector Stanley Hopkins comes to see Holmes at 221B Baker Street to tell him of a murder that defies solution. The dead man is Willoughby Smith, secretary to Professor Coram, an old invalid. The murder happened at Yoxley Old Place near Chatham, Kent. The most perplexing thing about the case to Hopkins is that it is apparently motiveless. Willoughby Smith seems to have nothing untoward in his background, and not an enemy in the world. He was the third secretary to the professor, the former ones not having worked out. The murder weapon was a sealing-wax knife belonging to the professor.
The maid found Smith, and the last words that he uttered as he lay dying were “The professor; it was she.” The professor, however, is a man.
This same maid told Hopkins while he was at Yoxley that she had heard Smith leave his room and walk down to the study. She had been hanging curtains and did not actually see him, only recognizing his brisk step. The professor was in bed at the time. A minute later, there was a hoarse scream from the study, and the maid, after hesitating for a moment, went there to find a murder scene. She later tells Holmes that Smith went out for a walk not long before the murder.
The murderer’s only likely means of entry was through the back door after walking along the path from the road, and Hopkins found some indistinct footmarks running beside the path, the murderer obviously having tried to avoid leaving a trail. Hopkins could not tell whether the track was coming or going, made by big or small feet. The road was a hopeless quagmire and nothing could be discerned there.
The professor’s study contained a bureau; nothing seemed to have been stolen. Its drawers were left open, as always, and the cupboard in the middle was locked. The professor kept the key.
One important piece of evidence was found in Willoughby Smith’s hand: a pair of golden pince-nez glasses. Holmes examines these and from them alone deduces several things about the murderer:
It is a woman;
She is of some good breeding;
She dresses like a lady;
She has a thick nose;
Her eyes are close together;
She has a puckered forehead, a peering look, and likely rounded shoulders;
She has been to an optician at least twice over the last few months.
She is a person of refinement, and is well dressed.
Holmes, Dr. Watson, and Hopkins all go to Yoxley the next day, and Holmes makes a careful examination of everything. In the study, he notices a recent scratch on the bureau, and reasons that the murderer’s purpose was actually to fetch something from in there. Smith was killed merely because he had interfered with a burglary. No-one saw the murderer leave, nor did anyone hear a door opening.
Holmes notes with some interest that both the corridors, the one leading from the back door and the one leading to the professor’s bedroom, are about the same length, and lined with coconut matting.
Holmes interviews the professor in his bedroom, smoking many Egyptian cigarettes while there, dropping the ashes everywhere. The professor claims utter ignorance as to what has happened in his house, and ventures the hypothesis that Smith’s death might have been suicide. Holmes asks about the locked cupboard in the bureau. The professor hands over the key. Holmes looks at it and then hands it back, not bothering to look in the bureau.
Shortly afterwards, Watson asks Holmes if he has a clue, and Holmes enigmatically replies that the cigarettes might show him.
Holmes meets the housekeeper in the garden and has a seemingly unimportant chat with her about the professor’s eating habits. Apparently he has been eating quite a lot today.
Early in the afternoon, the three men go back to see the professor in his room, and Holmes deliberately knocks the cigarettes over to provide an excuse for getting down on all fours on the floor. At this point, he solves the mystery, and the murderer, who looks exactly as Holmes deduced, emerges from a hiding place in a bookcase. Holmes has seen her tracks in the cigarette ashes.
The business unfolded thus: The woman came to the professor’s house to get hold of some documents, having obtained a duplicate key from one of the former secretaries. She came without the professor’s knowledge. She was surprised by Smith, whom she killed without meaning to, grabbing the nearest thing to defend herself — the sealing-wax knife. She lost her glasses in the scramble to escape, and was unable to see clearly. She turned along the wrong corridor and wound up in the professor’s room. Although surprised, he hid her. It turns out that she is the professor’s estranged wife, Anna, and they are both Russian. The documents in question would exonerate her friend in a Siberian prison. She and this friend had both been betrayed by the professor for gain, and she had also been sent to Siberia for a time.
Anna had met Smith while he was taking his walk, explaining Smith’s last words. The professor’s increased appetite is of course explained by his having to feed a second, hidden person.
At the end, Anna dies from poison she took before leaving her hiding place. As she dies, she asks Holmes to deliver the documents to the Russian Embassy, which he duly does.
I recommend this book to any reader that appreciates a well written mystery story. ( )

When I first knew about this case, I thought this is very mysterious and strange case.
There were someone's glasses at the scene of murder. Nobody hit upon the owner of that,
except Holmes. When he saw the glasses, he quickly describe about the murderer.He was too clever!
He tried to find the murderer by doing some investigete,and finally he found the murdere! The murdere was
hiding in the professor's room! This was really out of my expect! I was so surprised the appearance of the murderer!The murderer was a woman!
At the end, the murderer died by taking the poison. But before that, she asked a favor to Holmes. Considered her past, he
got her favor. At this part, I thought he was very kindly person! ( )