Steve went with this party and presently found himself with Kelly and another man speeding toward the building near the end of the row which he had seen the spy enter. From a broken sentence or two he learned that the system of search lights had just been installed, but not formally received from the contractor, and hence had not been turned on. That explained the first darkness of the yard. But there was little time for conversation and there was to be even less. For as they dashed up to the front of the building, the windows which before had been mere patches of blackness were sharply outlined now with the lurid, flickering glow of fire.

A savage snarl came from Kelly’s throat and he leaped for the door, master key in hand. The other man ran past him, pulled up at the corner, and yanked out his gun. Twice it spat fire, the echoes of the shots crashing through the silent yard with sharp distinctness.

“Get him?” snapped Kelly, flinging open the door.

“I did,” was the grim reply.

But it passed unheeded. Steve himself only recalled it afterward; for as the door swung open a cloud of smoke belched forth and behind it they could see a leaping, quivering wall of flame. At almost the same instant there came a blinding flash and the whole yard was bathed suddenly in a flood of clear, white light.

“The extinguisher, Joe—quick!” grated Kelly. “We’ve got to stop it before this wind takes hold.” He whirled on Steve. “Chase back to the bunkhouse, kid, and tell Dick to start the pumps and sound the alarm. Run!”

Steve ran, and long afterwards he had only to close his eyes to bring back every detail of that strange scene—for it was strange beyond description. The search lights had come on, and the wide road flanked with buildings was as brilliant as the busy street of any city, but as silent as the grave and as empty of any signs of life. And yet, to the boy, that surface emptiness and silence fairly pulsed with life—vivid, vital, elemental life, which might flame up, white hot, at any instant like the fire of a volcano bursting its thin crust of ashes. And as he ran Steve waited tingling, almost breathless, for that outbreak.

It came just as he reached the bunkhouse steps—a pistol shot, sharp and snapping. There was another and another still, and out of the tail of his eye he glimpsed indistinctly the swift dash of some figures past the rear of a building across the road. Racing up the steps, Steve panted out his message. In a moment more the piercing wail of a siren screamed shrilly through the night, followed quickly by the dull throbbing of machinery.

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.

He ran a few steps in that direction, slowed down for a lagging second or two, spurted again, and ducked around the corner of a big machine shop on the left of the road a little below the guard house. Back of this ran the completed portion of a high board fence topped with barbed wire which would ultimately encircle the entire yard. A moment before he had glimpsed, slipping along that fence, the figure of a man whose furtive movements roused instant suspicion. He might just possibly be one of the guards, but to Steve, remembering the three he had seen running that same way a little while before, it seemed much more likely that he was one of the spies heading for the end of the fence and freedom.