Bart.

"It must be that his own plane is injured and he has to descend," suggested Frank.

But there was no sign of injury to the descending plane and it seemed to be in perfect control. Swiftly and steadily it came down, and a cry of astonishment broke from the boys as they saw that it bore American markings.

"How's that?" exclaimed Frank. "There's been a fearful mistake somewhere. This fellow has downed a French plane thinking that it was German."

"He'll be court-martialed for that or I miss my guess," said Bart with a frown.

"It's bad enough to have the Huns after us without trying to kill our own people," growled Billy.

There was a level place nearby that made an ideal place for a landing, and the American machine came down there with scarcely a jar.

The boys rushed toward it with reproaches on their lips, but their wrath was lost in astonishment when they recognized, in the aviator who stepped forth, Dick Lever, one of the most daring of the American "aces" and a warm personal friend of theirs.

The reproaches died when they saw him, for only a little while before he had saved them from a German prison by swooping down with his machine and carrying them off from their captors. It was with mixed feelings that they greeted him, as he came gaily forward, a smile upon his handsome bronzed face. But Dick seemed to feel a certain stiffness in their welcome that was unusual.

"Hello, fellows," he greeted. "What's the grouch?"

"No grouch at all, Dick," answered Frank. "We owe you too much for that. We're only sorry that you happened to make a mistake and down a French plane thinking it was German."

Dick's eyes twinkled.

"Come out of your trance," he chuckled. "I don't make that kind of mistakes."

For answer Frank led the way to the wrecked and partly burned plane and pointed out the markings.