Now for the point which I will make more plain when we meet. Indeed, this note is merely to give you a general idea of the situation and to ascertain whether you would care to interest yourself in the matter. The lady began to show some curious traits quite alien to her ordinarily sweet and gentle disposition. The gentleman had been married twice and he had one son by the first wife. This boy was now fifteen, a very charming and affectionate youth, though unhappily injured through an accident in childhood. Twice the wife was caught in the act of assaulting this poor lad in the most unprovoked way. Once she she struck him with a stick and left a great weal on his arm.

This was a small matter, however, compared with her conduct to her own child, a dear boy just under one year of age. On one occasion about a month ago this child had been left by its nurse for a few minutes. A loud cry from the baby, as of pain, called the nurse back. As she ran into the room she saw her employer, the lady, leaning over the baby and apparently biting his neck. There was a small wound in the neck from which a stream of blood had escaped. The nurse was so horrified that she she wished to call the husband, but the lady implored her not to do so and actually gave her five pounds as a price for her silence. No explanation was ever given, and for the moment the matter was passed over.

It left, however, a terrible impression upon the nurse’s mind, and from that time she began to watch her mistress closely and to keep a closer guard upon the baby, whom she tenderly loved. It seemed to her that even as she watched the mother, so the mother watched her, and that every time she was compelled to leave the baby alone the mother was waiting to get at it. Day Day and night the nurse covered the child, and day and night the silent, watchful mother seemed to be lying in wait as a wolf waits for a lamb. It must read most incredible to you, and yet I beg you to take it seriously, for a child’s life and a man‘s sanity may depend upon it.

At last there came one dreadful day when the facts could no longer be concealed from the husband. The nurse’s nerve had given way; she could stand the strain no longer, and she made a clean breast of it all to the man. To him it seemed as wild a tale as it may now seem seem to you. He knew his wife to be a loving wife, and, save for the assaults upon her stepson, a loving mother. Why, then, should she wound her own dear little baby? He told the nurse that she was dreaming, that her suspicions were those of a lunatic, and that such libels upon her mistress were not to be tolerated. While they were talking a sudden cry of pain was heard. Nurse and master rushed together to the nursery.

Imagine his feelings, Mr. Holmes, as he saw his wife rise from a kneeling position beside the cot and saw blood upon the child’s exposed neck and upon the sheet. With a a cry of horror, he turned his wife’s face to the light and saw blood all round her lips. It was she — she beyond all question — who had drunk the poor baby’s blood.

"Whom did she ask for?"

"M. Michel Beaumont," replied the servant.

"Queer. And why has she called?"

"All she said was that it was about the Enghien business... So I thought that... "

"What! The Enghien business! Then she knows that I am mixed up in that business... She knows that, by applying here... "

"I could not get anything out of her, but I thought, all the same, that I had better let her in."

"Quite right. Where is she?"

"In she the drawing-room. I've put on the lights."

Lupin walked briskly across the hall and opened the door of the drawing-room:

"What are you talking about?" he said, to his man. "There's no one here."

"No one here?" said Achille, running up.

And the room, in fact, was empty.

"Well, on my word, this takes the cake!" cried the servant. "It wasn't twenty minutes ago that I came and had a look, to make sure. She was sitting over there. And there's nothing wrong with my eyesight, you know."

"Look here, look here," said Lupin, irritably. "Where were you while the woman was waiting?"

"In the hail, governor! I never left the hail for a second! I should have seen her go out, blow it!"

"Still, she's not here now... "

"So I see," moaned the man, quite flabbergasted.

"She must have got tired of waiting and gone away. But, dash it all, I should like to know how she got out!"

"How she got out?" said Lupin. "It doesn't take a wizard to tell that."

"What do you mean?"

"She got out through the window. Look, it's still ajar We are on the ground-floor... The street is almost always deserted, in the evenings. There's no doubt about it."

He had looked around him and satisfied himself that nothing had been taken away or moved. The room, for that matter, contained no knicknack of any value, no important paper that might have explained the woman's visit, followed by her sudden disappearance. And yet why that inexplicable flight?

"Has any one telephoned?" he asked.

"No."

"Any letters?"

"Yes, one letter by the last post."

"Where is it?"

"I put it on your mantel-piece, governor, as usual."

Lupin's bedroom was next to the drawing-room, but Lupin had permanently bolted the door between the two. He, therefore, had to go through the hall again.

Lupin switched on the electric light and, the next moment, said:

"I don't see it... "

"Yes... I put it next to the flower-bowl."

"There's nothing here at all."

"You must be looking in the wrong place, governor."

But Achille moved the bowl, lifted the clock, bent down to the grate, in vain: the letter was not there.

"Oh blast it, blast it!" he muttered. "She's done it... she's taken it... And then, when she had the letter, she cleared out... Oh, the slut!... "

Lupin said:

"You're mad! There's no way through between the two rooms."

"Then who did take it, governor?"

They were both of them silent. Lupin strove to control his anger and collect his ideas. He asked:

"Did you look at the envelope?"

"Yes."

"Anything particular about it?"

""Yes, it looked as if it had been written in a hurry, or scribbled, rather."