When Jane reached her own room, she stood a long time in front of the glass frowning at herself. It might be safe to look so exactly like a schoolgirl, but it was very, very humiliating. Henry had never glanced at her once. That, of course, was all in the line of safety too. Also, why should Henry look at her? Why should she wish him to do so? She was not in love with him; she had, in fact, refused him—could it be that there was a little balm in this thought? What did it matter to her how long he looked at Raymond Heritage?  
She took off the white muslin dress and put it away.
 
The worst part of being Renata was, not the risk, but having to wear Renata’s clothes. All the things were good, horribly good, and they were all quite extraordinarily dull. “If your shoes want mending, and your things are threadbare, every one knows it’s because you’re poor, and not because you like being down at heel and out at elbows. But Renata’s things must have cost quite a lot, and, of course, every one thinks they are my choice.”
 
By some deflected line of reasoning “every one” meant Henry.
 
 
Jane folded up the pale blue sash and shut it sharply into a drawer. Then she put on Renata’s dressing-gown. It was made of crimson flannel, very thick and soft, with scalloped edges to the collar and cuffs—“exactly like one’s grandmother’s petticoat.”
 
She rumpled the bedclothes and disarranged the pillows. Then she put out the light, sat down on the window-seat, and waited.
 
The blind was up; she had slipped behind the chintz curtains. The terrace lay beneath her, only half in shadow now. There was no sound in the house, no sound from the sea. The line of shadow moved backwards inch by inch.
 
When Jane sat down to wait, she told herself that she would not listen and strain; she would just sit there quite peacefully, and if anything was going to happen—well, let it happen. But as she sat there, she became afraid against her will, aware once more of that sense of pressure which had come upon her in the drawing-room. It was as if something was steadily approaching not her alone, but all of them—as if their thoughts and actions were being, at one and the same time, dictated by an outside force and scrutinised—watched—spied upon.
 
With all her might she resisted this sensation and the fear that it suggested. But, as the night passed to midnight and beyond, a strange feeling of being one watcher in a slumbering household detached itself from the general confusion, and she began to long with great intensity for something—anything—to happen.
 
 
Once something moved in the foot-wide strip of shadow against the house. Jane caught her breath and then saw that it was only a cat, a half-grown kitten rather, beloved of the cook. It came out into the moonlight and walked solemnly the entire length of the terrace with delicately taken steps and a high waving tail. It was as soundless and black as the shadow out of which it had come, and presently it was gone again, and second by second, minute by minute, slow, interminable, the night dropped away. In the hall a clock struck the quarters. The silence, shattered for a moment, closed again.
 
When the rapping came, it brought the oddest sense of interruption. Jane sprang to her feet, stood for a moment catching at her self-control, and then went noiselessly to the door. She listened before opening it, and could hear nothing; and, as she listened, the knocking came again, but from behind her.
 
Bewildered, she edged the door open and looked out. A shaded light burned far away to the left. The long, dim corridor was empty. She shut the door.
 
Some one was knocking—somewhere—but where?
 
She turned and stood facing the windows. Up in the far corner a large cupboard filled the angle and blunted it. Jane had hung her serge dress there hours and hours ago. The knocking seemed to come from the cupboard, just where the room was at its darkest because next the lighted window.
 
Jane crossed the floor very slowly, put both hands on the cupboard doors, and flung them wide. For a moment everything was quite black, then, with a most unpleasant suddenness, a narrow white ray cut the dark, and Henry’s voice said, “It’s only me.”
 
Jane’s hand went to her lips, pressing them firmly. She would not have admitted that this action alone saved her from screaming. After a moment she gave a little gasp, and located Henry, or rather Henry’s head, which was almost under her feet.
 
In the cupboard floor there was a square black hole, and, just above floor-level, Henry’s face looked up at her, tilted at an odd angle, whilst his one visible hand manipulated a small electric torch.
 
“Wait,” said Jane, in a whisper.
 
She went quickly to the door, locked it, removed the key, and put it in one of the dressing-table drawers. She did not know quite what made her do this, only suddenly when her eyes saw Henry, her mind had a vivid impression of that long corridor with its one faintly glimmering light.
 
Then she sat down on the cupboard floor, close to Henry’s head, and breathed out:
 
“Henry!—how on earth?”
 
Henry, who appeared to be standing upon a ladder or something equally vertical, came up a few steps, sat down on the edge of the hole, and switched off his torch.
 
“I had to see you,” he said. “This was my room in the old days, and Tony and I found this passage. It leads down to another cupboard in the garden room where they keep the tennis and croquet gear. How are you?—all right?”
 
“Yes, quite all right.”
 
“That’s good. Now which of us is going to talk first?”
 
“I think I had better,” said Jane. “You see, I saw Renata, and she told me things, and I think, if you don’t mind, Henry, that I had better tell you everything that she told me.”
 
“Yes, please.” He hesitated. “One minute, Jane, I just wanted to say, you don’t mind talking to me like this, do you? I wouldn’t have asked you to if there had been any other way—what I mean to say is....”
 
 
Jane gave a very small laugh, which was instantly repressed. She reflected that it was pleasanter to suppress a laugh than a scream.
 
“What you mean to say is, there aren’t any chaperons in this scene. You needn’t apologise, Henry. Sleuths never have chaperons—it’s simply not done; and, anyhow, I’m sure you’d make a beautiful one. Shall I go on?”
 
It may be doubted whether Henry really cared about being described as a chaperon. His tone was rather dry as he said:
 
“Go on, please.”
 
As for Jane, who had prodded him on purpose just to see if anything would happen, she certainly felt a slight disappointment accompanied by a sense of increased respect.
 
“You saw Renata. What did she tell you?”
 
“She told me what she overheard,” said Jane, speaking slowly. “Henry, if I tell you what it was, will you promise me not to let any one guess that you know? If they were certain that I knew, I shouldn’t be alive to-morrow; and if they thought you knew the secret, you’d never get back to London alive.”
 
“Who is ‘they,’ Jane?” said Henry.
 
“I want to tell you about Renata first. She really did walk in her sleep, you know. She must have waked when she opened the door. She said the first thing she knew was the cold feel of the hall linoleum under her feet. The door was open, and she was standing just on the threshold. There was a screen in front of her, and beyond the screen a man talking. She heard every word he said, and I am sure that what she repeated to me was just exactly what she heard. The first words that she caught were ‘Formula “A.”’”
 
 
Henry gave a violent start.
 
“Good Lord!” he said under his breath. “You’re sure?”
 
“Quite. Then he went on, and this is what he said: ‘You all have Formula “A.” You will go to your posts and from your directions you will prepare what is needful according to that formula, carrying out to the last detail the cipher instructions which each of you has received. As soon as the experiments relating to Formula “B” are completed, you will receive a summons in code. You will then assemble at the rendezvous given, and Formula “B,” with all instructions for its employment, will be entrusted to you. With Formula “A” you have the key. When Formula “B” is also complete you will have the lock for that key to fit; then the treasures of the world are yours. The annihilation of civilisation and of the human race is within our grasp. When the key has turned in the lock we only shall be left, and....’ Just then, Renata said, some one else cried out, ‘The door! The door!’ They pushed the screen away and pulled her in. She nearly fainted. When she revived a little, her father and Mr. Ember were trying to find out what she had heard. Fortunately for herself, she told me, at first it was all confusion. The only thing that stood out clearly was that shout at the end, but afterwards, when she was alone, it all came back. She said it was like a photographic plate developing, hazy at first, and then everything getting clearer and sharper until each detail came out. She repeated the whole thing as if it were a lesson.”
 
“Wait,” said Henry. “My head’s going round. I want to sort things out.”
 
 
Jane waited. She had been prepared for Henry to be impressed or incredulous. What took her by surprise was the puzzled note in his voice. “Lord, what a mix-up!” she heard him say.
 
Then he addressed her again.
 
“Did you ever play ‘Russian Scandal,’ Jane?” he said.
 
“Yes, of course. But if you had heard Renata—the sort of queer mechanical way she spoke, exactly like a gramophone record—why, the words weren’t words she’d have used, and all that about Formula ‘A’—do you think that’s the sort of thing that a schoolgirl makes up?”
 
“No,” said Henry unexpectedly. “I think it is quite possible that she overheard something about Formula ‘A,’ and I’d give a good deal to know just what she did hear.”
 
“I’ve told you what she heard,” said Jane. “Jimmy always said I had a photographic memory, and I said the whole thing over to myself until I had it by heart. You see, I didn’t dare to write it down.”
 
“Can you say it again?” said Henry. “I’d like to get it down in black and white, and have a look at it. At present it makes me feel giddy.”
 
“You mustn’t write it down,” said Jane breathlessly. “Oh, you mustn’t, Henry! It’s not safe.”
 
Henry turned on his torch, propped it against the wall, and produced a notebook and a pencil. The cold, narrow beam of light showed his knee, the white paper, a pencil with a silver ring, and Henry’s large, brown hand.
 
“He has a horribly determined hand,” thought Jane.
 
 
“Now,” said Henry, “will you start at the beginning and say it all over again, please?”
 
Jane did so meekly, but her inward feelings were not meek. Once more she repeated, word for word, and sentence for sentence, the somewhat flamboyant speech of Number Four.
 
Henry’s hand travelled backwards and forwards in the little lane of light, and, word for word, and sentence by sentence, he wrote it down. When he had finished, he read over what he had written. If he had not a photographic memory, he was, at any rate, aware that Jane in her repetition had not varied so much as a syllable from her first statement.
 
He went on looking at what he had written. At last he said:
 
“Jane, I think I must tell you something in confidence. Sir William, as you know, is conducting important experiments for the Government. How important you may perhaps have gathered from the extraordinary precautions which are taken to prevent any leakage of information. These experiments have resulted in two valuable discoveries represented, for purposes of official correspondence, by the terms Formula ‘A’ and Formula ‘B.’ Within the last week we have had indisputable proof that Formula ‘A’ has been offered to a foreign power. That is the reason for my presence here. Now these are facts. Let them sink into your mind, then read over what I have just taken down, and tell me how you square those facts with Renata’s statement.”
 
Jane picked up the notebook, stared at the written words, set Henry’s facts in the forefront of her mind, and remarked candidly:
 
“It does make your head go round rather, doesn’t it?”
 
Henry assented. They both sat silent. Then Jane put down the notebook.
 
“Never mind about our heads going round,” she said. “Let me go on and tell you the rest of it. It isn’t only what Renata heard; it’s the things that keep happening—little things in a way, but oh, Henry, sometimes I think they are more frightening just because they are little things. I mean, supposing you know you’re going to be executed, you brace yourself up, and it’s all in the day’s work, but if you are out at a dinner-party and you suddenly find poison in the soup, or a bomb in the middle of the table decorations, it’s ... well, it’s unexpected—and, and perfectly beastly.”
 
Jane’s voice broke just for an instant.
 
Henry’s hand came quickly through the torchlight, and rested on both hers. It was a satisfactorily large and heavy hand.
 
She told him about her interview with Ember at the flat, and one by one she marshalled all the small happenings which had startled and alarmed her.
 
Henry waited until she had quite finished. Then he said:
 
“This lip-reading—you know, my dear girl, it’s a chancy sort............