"Pass," said the sentry, who was not in uniform, and carried a revolver instead of a rifle.
And then, a few paces further on, they came to a strange mass covered with canvas. A man stepped out of the shadow, flashing an electric torch in their faces.
"Stepan? That is good!" he said.
Stepan went forward and drew off the canvas cover, and Dick saw what was underneath—a monoplane, as he had guessed!
"That is a captured Austrian 'plane," said Stepan. "Now do you understand? Are you willing to take the risk of flying in it with me?"
"I wouldn't miss it!" said Dick. "But I didn't know you knew how to run one!"
"He is one of our very few qualified aviators," said the man who had been on guard. "And every day now for weeks he has been coming here to study the controls and all the details of this machine. It is in perfect order, ready to take the air."
"And an Austrian monoplane! Why, we can fly over their lines!" exclaimed Dick. "How splendid! But what are you to do, Steve?"
"You will soon know. Get aboard! Your seat is there. Strap him in, Dmitri, while I see to the tank."
"Everything is right," said Dmitri. "But make sure for yourself—that is a good rule."