Henri had some difficulty in keeping a serious face when Billy offered this plea as an excuse for the performance that had almost brought nervous prostration to Salisky and Marovitch, the dispatch bearers.

In a quiet corner later on, Henri had no desire to even smile when Billy gravely reviewed the possibility of the vengeful Cossack tracing them to Warsaw.

“You know,” said the boy from Bangor, “those fellows hang on like grim death when they have a grudge against anybody, and this wild and woolly scout is evidently anxious to stick his claws into us.”

“Maybe after all,” suggested Henri, “it is just because he thinks we are spies, having seen us working with or, rather, for the other side.”

“Why, then, didn’t he make his spring when we were within easy reach?”

“You forget, Billy,” replied Henri, “that by the time he had patched up his memory we were in Malinkoff palace, and even the tiger of the plains would hesitate before attempting to rough it with a Russian duke.”

“And there was a good reason why he did not have it out with us when we left the palace,” added Billy.

“A backway reason,” concluded Henri.

The Russian secret service, reputed to be a wonderfully efficient system, had now advices of the activities of that eminent arch-schemer, Roque, or whatever other name by which he was known, in this section of the war zone.

The blowing up of the war depot in Warsaw was less a mystery since the authorities had learned of the presence of this dreaded operator even so close as the width of a river.