Admission had been gained by the front door; there was a tradesman who saw a man let himself into the house, carrying what looked to be a fishing-rod under his arm, but which undoubtedly was a rifle in a cloth case.

    "Very simple," said Dick; "and, of course, from the Frog's point of view, effective. The shooter had half-a-dozen ways, of escape, including the fire-escape."

    Elk was silent and glum. Dick Gordon as silent, but cheerful, until the two men were back in his office.

    "It was my inquiry at the garage that annoyed them," he said, "and I'll give them this credit, that they are rapid! I was returning to my house when the first attempt was made. The most ingenious effort to run me down with a light car—the darned thing even mounted the pavement after me.

    "Number?"

    "XL.19741," said Dick, "but fake. There is no such number on the register. The driver was gone before I could stop him."

    Elk scratched his chin, surveying the youthful Public Prosecutor with a dubious eye.

    "Almost sounds interesting to me," he said. "Of course I've heard of the Frogs, but I didn't give much attention. Nowadays secret societies are so common that every time a man shakes hands with me, he looks sort of disappointed if I don't pull my ear or flap my feet. And gang work on a large scale I've always looked upon as something you only hear about in exciting novels by my old friend Shylock—"

    "Sherlock—and he didn't write them," murmured Dick.

    Again Elk fingered his cheek.

    "I don't believe in it, anyway," he said after thought. "It's not natural that tramps should do anything systematic. It's too much like work. I'll bet there's nothing in it, only a lot of wild coincidences stickin' together. I'll bet that the Frogs are just a silly society without any plan or reason. And I'll bet that Lola knows all about 'em," he added inconsistently.

    Elk walked back to "The Yard" by the most circuitous route. With his furled and ancient umbrella hanging on his arm, he had the appearance of an out-of-work clerk. His steel-rimmed spectacles, clipped at a groggy angle, assisted the illusion. Winter and summer he wore a soiled fawn top-coat, which was invariably unbuttoned, and he had worn the same yellowish-brown suit for as long as anybody could remember. The rain came down, not in any great quantities, but incessantly. His hard derby hat glistened with moisture, but he did not put up his umbrella. Nobody had ever seen that article opened.

    He walked to Trafalgar Square and then stopped, stood in thought for some time, and retraced his steps. Opposite the Public Prosecutor's office stood a tall street-seller with a little tray of matches, key-rings, pencils and the odds and ends that such men sell. His wares, for the moment, were covered by a shining oil-cloth. Elk had not noticed him before, and wondered why the man had taken up so unfavourable a stand, for the end of Onslow Gardens, the windiest and least comfortable position in Whitehall, is not a place where the hurrying pedestrian would stop to buy, even on a fine day. The hawker was dressed in a shabby raincoat that reached to his heels; a soft felt hat was pulled down over his eyes, but Elk saw the hawk-like face and stopped.

    "Busy?"

    "Naw."

    Elk was immediately interested. This man was American, and was trying to disguise his voice so that it appeared Cockney—the most impossible task that any American had ever undertaken, for the whine and intonation of the Cockney are inimitable.

    "You're American—what state?"

    "Georgia," was the reply, and this time the hawker made no attempt at disguise. "Came over on a cattle boat during the war."

    Elk held out his hand.

    "Let me see that licence of yours, brother," he said.

    Without hesitation the man produced the written police permit to sell on the streets. It was made out in the name of "Joshua Broad," and was in order.

    "You're not from Georgia," said Elk, "but that doesn't matter. You're from Hampshire or Massachusetts."

    "Connecticut, to be exact," said the man coolly, "but I've lived in Georgia. Want a key-ring?"

    There was a gleam of amusement in his eyes—the merest flash.

    "No. Never had a key.