Back in the road again, the boy paused for an instant, his heart beating fast with excitement. The sense of empty quiet had vanished utterly. Above him, from the engine-house stack, the high, piercing note of the siren rose and fell shrieking a clamorous warning. From somewhere in the yard a rifle shot came sharply to his ears. Ahead of him several guards were thudding down the road towards the clouds of red-tinged smoke which poured from the burning building with increasing volume.