“Shout, Frog, and I’ll throttle you,” hissed the detective ferociously. There was no scuffle, no sound. The thing was done so quickly that, if there were other watchers in the street, they could not have known what had happened, or have received any warning from their comrade’s fate. The man was in the hands of the following detective, gagged and handcuffed, and on his way to the police car, before he knew exactly what tornado had struck him. “Do you mind if I sing?” said Elk as they turned into the street on the opposite side to that where Mr. Maitland’s late residence was situated. Without waiting permission Elk broke into song. His voice was thin and flat. As a singer, he was a miserable failure, and Dick Gordon had never in his life listened with so much patience to sounds more hideous. But there would be watchers at each end of the street, he thought, and soon saw that Elk’s precautions were necessary. Again it was in the shadow of a street-lamp that the sentinel stood—a tall, thickset man, more conscientious in the discharge of his duties than his friend, for Dick saw something glittering in his mouth, and knew that it was a whistle. “Give me the woild for a wishing well,” wailed Elk, staggering slightly, “Say that my dre-em will come true . . .” And as he sang he made appropriate gestures. His outflung hand caught the whistle and knocked it from the man’s mouth, and in a second the two sprang at him and flung him face downward on the pavement. Elk pulled his prisoner’s cap over his mouth; something black and shiny flashed before the sentry’s eyes, and a cold, circular instrument was thrust against the back of his ear. “If you make a sound, you’re a dead Frog,” said Elk; and that portion of his party which had made the circuit coming up at that moment, he handed his prisoner over and replaced his fountain-pen in his pocket. “Everything now depends upon whether the gentleman who is patrolling the passage between the gardens has witnessed this disgusting fracas,” said Elk, dusting himself. “If he was standing at the entrance to the passage he has seen it, and there’s going to be trouble.” Apparently the patrol was in the alleyway itself and had heard no sound. Creeping to the entrance, Elk listened and presently heard the soft pad of footsteps. He signalled to Dick to remain where he was, and slipped into the passage, walking softly, but not so softly that the man on guard at the back gate of Mr. Maitland’s house did not hear him. “Who’s that?” he demanded in a gruff voice. “It’s me,” whispered Elk. “Don’t make so much noise.” “You’re not supposed to be here,” said the other in a tone of authority. “I told you to stay under the lamp-post——” Elk’s eyes had grown accustomed to the darkness, and now he saw his man. “There are two queer-looking people in the street: I wanted you to see them,” he whispered. All turned now upon the discipline which the Frogs maintained. “Who are they?” asked the unknown in a low voice.