Stupidly the man obeyed. A leather pocket-case came from an inside pocket and this Beale opened.

Therein was a small packet which resembled the familiar wrapper of a seidlitz powder. Beale spoke sharply in a language which the girl realized was German, and the man shook his head. He said something which sounded like "No good," several times.

"I'm going to leave you here alone for awhile," said Beale, "my friend and I are going downstairs together--I shall not be long."

They went out of the flat together, the little man with the big head protesting, and she heard their footsteps descending the stairs.

Presently Beale came up alone and walked into the sitting-room. And then the strange unaccountable fact dawned on her--he was perfectly sober.

His eyes were clear, his lips firm, and the fair hair whose tendencies to bedragglement had emphasized his disgrace was brushed back over his head. He looked at her so earnestly that she grew embarrassed.

"Miss Cresswell," he said quietly. "I am going to ask you to do me a great favour."

"If it is one that I can grant, you may be sure that I will," she smiled, and he nodded.

"I shall not ask you to do anything that is impossible in spite of the humorist's view of women," he said. "I merely want you to tell nobody about what has happened to-night."

"Nobody?" she looked at him in astonishment. "But the doctor----"

"Not even the doctor," he said with a twinkle in his eye. "I ask you this as a special favour--word of honour?"

She thought a moment.

"I promise," she said. "I'm to tell nobody about that horrid man from whom you so kindly saved me----"

He lifted his head.

"Understand this, Miss Cresswell, please," he said: "I don't want you to be under any misapprehension about that 'horrid man'--he was just as scared as you, and he would not have harmed you. I have been waiting for him all the evening."

"Waiting for him?"

He nodded again.

"Where?"

"In the doctor's flat," he said calmly, "you see, the doctor and I are deadly rivals. We are rival scientists, and I was waiting for the hairy man to steal a march on him."

"But, but--how did you get in."

"I had this key," he said holding up a small key, "remember, word of honour! The man whom I have just left came up and wasn't certain whether he had to go in No. 8, that's the doctor's, or No. 6--_and the one key fits both doors!_"

He inserted the key which was in the lock of her door and it turned easily.

"And this is what I was waiting for--it was the best the poor devil could do."

He lifted the paper package and broke the seals. Unfolding the paper carefully he laid it on the table, revealing a teaspoonful of what looked like fine green sawdust.

"What is it?" she whispered fearfully.

Somehow she knew that she was in the presence of a big elementary danger--something gross and terrible in its primitive force.

"That," said Mr. Beale, choosing his words nicely, "that is a passable imitation of the Green Rust, or, as it is to me, the Green Terror."

"The Green Rust? What is the Green Rust--what can it do?" she asked in bewilderment.

"I hope we shall never know," he said, and in his clear eyes was a hint of terror.

CHAPTER III

PUNSONBY'S DISCHARGE AN EMPLOYEE

Oliva Cresswell rose with the final despairing buzz of her alarm clock and conquered the almost irresistible temptation to close her eyes, just to see what it felt like. Her first impression was that she had had no sleep all night. She remembered going to bed at one and turning from side to side until three. She remembered deciding that the best thing to do was to get up, make some tea and watch the sun rise, and that whilst she was deciding whether such a step was romantic or just silly, she must have gone to sleep.

Still, four hours of slumber is practically no slumber to a healthy girl and she swung her pyjama-ed legs over the side of the bed and spent quite five minutes in a fatuous admiration of her little white feet.

With an effort she dragged herself to the bath-room and let the tap run.

Then she put on the kettle. Half an hour later she was feeling well but unenthusiastic.

When she became fully conscious, which was on her way to business, she realized she was worried. She had been made a party to a secret without her wish--and the drunken Mr. Beale, that youthful profligate, had really forced this confidence upon her. Only, and this she recalled with a start which sent her chin jerking upward (she was in the bus at the time and the conductor, thinking she was signalling him to stop, pulled the bell), only Mr. Beale was surprisingly sober and masterful for one so weak of character.

Ought she to tell the doctor--Dr. van Heerden, who had been so good a friend of hers? It seemed disloyal, it was disloyal, horribly disloyal to him, to hide the fact that Mr. Beale had actually been in the doctor's room at night.

But was it a coincidence that the same key opened her door and the doctor's? If it were so, it was an embarrassing coincidence. She must change the locks without delay.

The bus set her down at the corner of Punsonby's great block. Punsonby's is one of the most successful and at the same time one of the most exclusive dress-houses in London, and Oliva had indeed been fortunate in securing her present position, for employment at Punsonby's was almost equal to Government employment in its permanency, as it was certainly more lucrative in its pay.

As she stepped on to the pavement she glanced up at the big ornate clock. She was in good time, she said to herself, and was pushing open the big glass door through which employees pass to the various departments when a hand touched her gently on the arm.

She turned in surprise to face Mr. Beale, looking particularly smart in a well-fitting grey suit, a grey felt hat and a large bunch of violets in his buttonhole.

"Excuse me, Miss Cresswell," he said pleasantly, "may I have one word with you?"

She looked at him doubtfully.

"I rather wish you had chosen another time and another place, Mr.

Beale," she said frankly.

He nodded.

"I realize it is rather embarrassing," he said, "but unfortunately my business cannot wait. I am a business man, you know," he smiled, "in spite of my dissolute habits."

She looked at him closely, for she thought she detected a gentle mockery behind his words, but he was not smiling now.

"I won't keep you more than two minutes," he went on, "but in that two minutes I have a great deal to tell you. I won't bore you with the story of my life."

This time she saw the amusement in his eyes and smiled against her will, because she was not feeling particularly amused.