With a flare on the compass, rising high, Billy held the nose of the biplane in the direction of the heights that centered headquarters.
Small red sparks glowed in the trenches below, and the upper darkness was ever and anon split by signal rockets and leaping flames of light from countless campfires.
Billy, with the aid of the small searchlight in the bow of the biplane, found safe landing, also insuring a sight of the colors to the sentries, who might otherwise be tempted to take a pot shot at the winged, midnight visitor.
Henri was the first to hear the whirr of the incoming aircraft, for which he had for hours held an open ear.
"Here you are at last!" he exclaimed, making an open-arm break for his flying partner. "You haven't lost an eye, or a leg, or anything, have you?" he anxiously inquired.
"Sound as an Uncle Sam dollar, old boy," assured Billy. "But you just bet I'm sleepy."
"I believe even Roque was uneasy about you," said Henri, as he insisted on giving Billy's blanket a snug tug.
That the secret agent proposed to reserve the services of the young aviators to himself thereafter and during their stay in this locality was made manifest when he told them the next day to make ready for a quick departure in the biplanes. As usual, he furnished no advance particulars.
It appeared that Schneider was also to figure in the expedition in a capacity indicated by his employment of oiling and polishing a service rifle of the 16-shot brand, and the display of a pair of long-barreled revolvers stuck in his belt.
"He looks like an arsenal on parade," commented Billy when the red-haired flyer, in war-like array, passed on the way to conference with Roque.