“Yes,” he growled hoarsely. “I accept your terms. It is a bargain.”

“On your honour?”

“On my word of honour as a Prussian officer and a gentleman.”

“Well, then, hurry up and open this door. It is getting stifling in here; and, besides, Rebener will be growing anxious about me.”

“But, first, your information. Where is the instrument?”

“Oh, the instrument?” It was now Edestone’s turn to laugh. “Why, that is lying on the floor under the table in Mr. Rebener’s dining-room. I dropped it there, when I came out to answer your telephone call, and I also gave instructions to the sentries on guard at the door of the apartment to shoot any one who attempted to pass in or out during my absence. You are doubtless a brave man, but I do not think you are prepared to tackle a whole company of British cavalry.

“And now,” he concluded, “I have kept to my bargain. Will you kindly open the door?”

A muttered German imprecation, like a snarl of baffled chagrin, was his only answer. But a moment later the door to his booth swung open, and he was free.

As he stepped out, he found the lights in the room turned on, and the man at the switchboard gone. He also noticed that the door to the adjoining booth was shaking, as if someone had just jerked it open and had passed out hurriedly, and, as he came out into the corridor, he thought he glimpsed the figure of a man hastily disappearing down the staircase. So far as any other evidence went, except for his wilted collar and heaving lungs, the whole experience might have been a dream.

He returned quietly to the dinner table, and stooping over, as if to pick up his napkin, recovered the instrument and slipped it into his trousers pocket.