"Listen—listen! There's somebody coming."
The others ceased speaking, and a strange, oppressive silence seemed to hover over the chamber.
Then, almost instantly, there came sounds which indicated that several people were approaching along the passageway.
"We are discovered!" exclaimed Dunstan, grim humor in his tone. "Ah, fellows, our sensational exploit must be revealed to a gaping world sooner than we expected!"
Simultaneously, the three sprang to their feet and made for the doorway.
Beyond the beams of Don Hale's flash-light the passageway was illuminated by the yellow glow of a lantern carried by the leader of a dim and shadowy group.
Anxiously—expectantly—the ambulanciers waited, while the sound of voices, steadily growing louder, echoed through the subterranean retreat.
And one of them made Chase Manning give a loud gasp of surprise.
"Well, well, can you beat that!" he exclaimed, clutching Don Hale tightly by the arm.
"Who is it?" asked Don. But the question needed no answer from Chase. For at that moment the lantern, swung high, illuminated the face of the man who carried it, and the boys recognized the "mysterious poilu."