Frank and his companions got up on the rocks and watched the distant vessel very closely.

They imagined, of course, that she was one of Captain Diavolo’s fleet, and resolved to pounce upon her at the earliest opportunity after learning her intention.

The airship was then at least twenty leagues from the retreat of the pirates, for the long search they had for the vessel that carried Leon away had taken them far from the lair of the Coast Terrors.

“Zamora, you heard Diavolo say he had two schooners and a steamer.”

“Exactly so,” returned the dark-faced Mexican.

“Does that look like one of their ships?”

“Decidedly not. It looks more like a frigate.”

“That’s a fact. How queer!”

“I don’t know what to make of it.”

When the vessel got nearer they saw that she really was a man-of-war, but failed to recognize her nationality.