"Stanny" had already made good with the American boy, not so much by his frank expression of admiration for the youngster's handling of the military biplane as for the reason that the Austrian talked plain United States when they were alone. Billy was dead-set against the trial of eternally groping for the meaning of foreign phrases. "Do you know why we aviators are running a freight line just now?" queried this new friend. Billy acknowledged that he had not the least idea on that subject. "Why?" "Filimonoff." "Who in the dickens is Filimonoff?" "He is the greatest of all Cossacks," explained the senior airman, "and the very devil on two sticks. Near Przemysl, not long ago, he held up one of our convoys and captured 200 wagons of grain and coal. He strikes where least expected, plays the peasant to perfection and secretly gets a lot of information that does not belong to him. It would be worth a lot to a fellow who dulled the spurs of this cock of the walk." "Ah hum," thought Billy, "I can pretty near guess now what brought Roque to this neck of the woods." So long was the enforced wait at headquarters this day that it was not until after nightfall that the biplane set out on its return voyage to the fortress. A strong air current from the north, with a decided snap to it, forced the aviators out of fixed course, but despite the biting blast Stanislaws was yet able to advise the pilot as to the general direction to be pursued. They saw ahead of them a red glow and the uplift of a spreading fountain of sparks. It was a house burning to the ground, probably fired by a Russian shell. The blaze revealed a familiar landmark to the biplane observer. "Keep her nose to the left," he advised the pilot. Billy, who figured the speed fully 70 miles to the hour, had the machine under perfect control, and it instantly responded to every shift of the steering lever. With the ordered slight turn it was scarce ten minutes before the biplane hovered over the vast, shadowy mass of the fortress below. The powerful propeller stopped, and the winged racer stood still against the black dome of the midnight sky. Now the forward plane dipped as the throbbing of the motor again was heard, and the bird machine plunged down at an angle of 45 degrees, settling in the plaza within the silvery ring formed by its own searchlight. "The work of an artist," proclaimed Stanislaws to the aviators in the night watch. "Carrying some weight, too," added the soldier who superintended the removal of the cargo. Billy had a bedtime story for Henri about Filimonoff. It having been determined to regularly use both biplanes in the carrying service, the detail at last put the boys together in the same machine, with Stanislaws and Schneider manning the other. "None of your self-made adventures," Roque admonished, when he had informed Billy and Henri of the arrangement.