“Oh!” cried the girl, with an exclamation that was half a sob, “oh, what good fortune.  So he was keeping that as evidence against me, eh?  Well, perhaps this accident was providential, after all.”

She picked up the comb and then turned her attention to the wallet.  Giving a quick glance around to see that she was unobserved the girl plunged her white fingers into the pocket case.  They encountered something crisp and crackly.  She drew the object out.

“A twenty-dollar bill!” she exclaimed wonderingly, “and nothing else.  I wonder if this can have anything to do with——.”

She was turning it over curiously as she spoke.  Suddenly a red spot flamed up in her either cheek.

“It’s marked with a red round O,” she exclaimed, “what a bit of evidence.  So Master Roy Prescott, you were planning to unmask me by that side-comb, were you?  Well, I shall play the same trick on you with this bill.”

Fanning Harding was coming back at that moment with the cup full of water.  The girl checked him with an excited gesture.

“Fortune has played into our hands,” she cried, “look here!”

“Well, what is it?” asked Fanning, rather testily.

“This bill.  Don’t you see it’s one of the stolen ones.  Look at the red circle upon the back.”

“Jove!  So it is.  But, what, how——­”

“Hush!  Don’t talk so loud.  This wallet, which contained it, was jolted out of Roy Prescott’s pocket when he was hurled from the machine.  The wallet and—­and something else.  But don’t you see what power that gives us?”

“No.  I confess I’m stupid, but——­”

“Oh, how dense you boys are,” exclaimed Regina, with an impatient stamp of the foot, “don’t you see that this bill will come pretty close to proving Roy Prescott a thief, if we want to use it that way?  You are a witness that I found it in his wallet which had been jerked out of his pocket.  Isn’t that enough?”

“Well, men have been sent to prison on less evidence,” said Fanning, with a shrug; “but I’ve got to hurry up with this water or they’ll suspect something.  I’ll talk more with you about this later on.  Your father and mine need every bit of fighting material they can get hold of, if we are to win the big prize for the Mortlake aeroplane.”

A shadow fell athwart the road as Fanning, an evil smile on his flabby, pale face, hastened down into the depression in which Roy, with Peggy bending above him, still lay.  The girl looked swiftly up.  A big, red aeroplane was hovering on high.  Presently one of its occupants, a girl peered over the edge.  The next minute she turned and said something in an excited tone to her companion.  The aeroplane began to drop rapidly.  In a few seconds it came to earth in the roadway, not a stone’s throw from the wrecked auto and its uninjured Blue Bird comrade.

The new arrivals were Jimsy and Jess.  They had set out on a sky cruise to the Prescott home, and Jess’s bright eyes had espied the confusion in the road beneath them as they flew over.  The swift descent had been the result.