So intent were the lads upon their conversation, that they mistook another freight shed for the one beneath which the Mermaid was hidden, and walked a few paces beside it before discovering their error. When they did so, they at once began to retrace their steps, and in turning a corner of the building came plump upon a cloaked figure evidently on their trail.
"Hello! what do you mean, sir, by following us?" cried Carl Baldwin, seizing the stranger's arm as he spoke.
With a muttered oath the man wrenched himself free and darted away, but not before the gleam of a street light had revealed his features to Carlos Moranza.
"The very fellow who tried to force his way into the quarters of the Junta!" he exclaimed, "and more than likely a Spanish spy. It is a narrow escape, my Carol, for if our blunder had not forced us to turn back, he must have discovered the Mermaid. In that case we should indeed have met with trouble."
"Let us hasten, then, before he returns."
"I don't believe he will dare do that. He is too badly scared."
But the spy did return, and, crouching in deepest shadow, became convinced that those whose business he was so anxious to discover had passed beneath the wharf. As he dared not attempt to follow them through the impenetrable gloom into which they had disappeared, he sought a hiding-place, and from it watched with infinite patience for them to again come forth.
They had, in the meantime, safely regained the snug living-room of the Mermaid, and reported all that had happened, to the Professor. Then Carl Baldwin unfolded his scheme for delaying the Spanish cruiser in port until after their departure.