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.
as a result, the submarine boat was allowed to drift down the harbour with the ebbing tide, until she came abreast the great black hull of a man-of-war. then she imperceptibly sank beneath the surface.
"she hovered like a gigantic fish."
the watch officer of the spanish cruiser, leaning on her after-rail and gazing musingly down into the dark waters sweeping seaward, speculated idly concerning the stream of phosphorescent light tailing out from under her counter, but thought of it only as a natural phenomenon. had he known that it was caused by the motion of the mermaid's propeller necessary to hold her in position against the stream while she hovered like a gigantic fish directly above the screw of his ship, how easily could he have won the promotion for which he longed. but he suspected nothing; and as carl baldwin, working from the diving chamber of the submarine craft, had succeeded in fastening one end of a short length of stout wire rope to the propeller blade, and shackling the other to a ring-bolt in the massive rudder, the officer turned with a sigh and walked away.
on the following morning the spanish spy, weary and cramped with his long vigil, was amazed to see an utter stranger emerge cautiously from beneath the wharf he had been watching, and walk quickly away. for a moment the spy was undecided as to whether he should follow this person or seek to discover where he had come from. then choosing the former course, he followed professor rivers at a respectful distance, until he had the vast satisfaction of seeing him meet, near the custom-house, the captain of the tug that was avowedly bound for havana.
there was a connection then between those who hid beneath the wharf and the suspected tow anchored in the harbour. undoubtedly a store of contraband goods was concealed under the wharf, and an effort would be made to convey them on board the tug before she sailed. what a reward was in prospect for him could he but discover it!
a little later the spy, with two companions, all armed, occupied a skiff that made its way cautiously through the dark spaces beneath the wharf he had watched so long. suddenly between them and the outer daylight two men appeared one after the other. both slid down one of the piles supporting the pier and dropped into the water, or at least the exulting spy thought they did so as he hastily urged his boat in that direction.
to his amazement and disgust, when he reached the spot where they had disappeared, he could discover no trace of them. neither was there a boat or a hiding-place into which they could have gone. the man was furious at being thus baffled, and uttered many a fierce spanish oath. finally, convinced that further search in that direction was fruitless, he pulled out into the harbour to watch the mysterious tow that still lay at anchor. as he drew near to it he saw its captain come off from shore alone. then the guard from one of the revenue cutters was withdrawn, anchors were lifted, and the tow began to move slowly down the channel. it was certain that no one save the captain had gone aboard, nor had any cargo been taken in except a few tons of carefully examined coal.
never in his life had the spy been so puzzled and disappointed; but it was a slight consolation to know that spain's vigilant cruiser would accompany the gringos to havana. even now was the black-hulled warship preparing to follow the departing tow. as the massive anchor broke away from the bottom, her great screw began to churn the water, and she slowly forged ahead. suddenly her screw ceased to act, she took a sheer in the wrong direction, there was a vast amount of confusion on her decks, and in another minute she was fast aground on a bank of the narrow channel. every eye in key west harbour was fixed upon her, and before any one again thought of the departing tow, it had gained the high seas, and was beyond the jurisdiction of either spain or "uncle sam." a little later, with the saucy mermaid safely hidden in the ample receptacle of the great dumping scow, the tow had vanished in the direction of havana.
that night the spy boarded a swift passenger steamer bound for the same port, which at sunrise of the following morning passed beneath the frowning walls of moro castle in company with the tow he had come to watch.
the mermaid retained her berth even after a pilot had boarded the tug, and her crew looked eagerly upon the wonderfully beautiful scene unfolding before them as they passed through a narrow entrance into the broad, landlocked harbour of havana.
carl baldwin, to whom everything was excitingly novel, viewed with delight the grim moro with its tall lighthouse tower, the white cabanas fortress, the tinted, flat-roofed buildings of the city across the placid basin, the quaint cathedral spires, and the thousand other curious features of spain's chief stronghold in the new world.
carlos moranza, filled with conflicting emotions at again approaching his native land under such strange conditions, gazed in silence, but as though hoping with the very intensity of his vision to pierce the crowding walls and discover the prison of his beloved sister.
professor rivers had eyes only for the warships, of which the harbour held half-a-dozen, as he speculated upon the ease with which his little mermaid could humble their pride and render them powerless.
at this very moment the spanish spy was regarding, and triumphantly recognising, all three of the americans through a glass levelled at them from the deck of the steamer on which he was a passenger. thus it happened that, as the captain of the tug was preparing to go ashore and make formal entry at the custom-house, after having successfully passed examination by both health officers and port authorities, two barges filled with soldiers dashed out from the mole and headed directly towards the new arrivals. one of these took possession of the tug, while the other, in which sat the exulting spy, ranged alongside the dumping scow.
for nearly an hour the soldiers searched every compartment and corner of the two vessels, even overhauling the coal in the tug's bunkers. when there was no longer an unexplored crevice, even the spy was forced to confess that there was no person aboard unaccounted for in the tug's papers, and that he must have laboured under a delusion as to what he had seen. he was bewildered, mortified, and angry, and was rendered furious by the ridicule heaped upon him by the officer to whom he was obliged to report his failure to discover anything that would justify a seizure of the tug.
this craft the spaniards would have been glad to possess, but when its captain went ashore and announced his desire to dispose of the dumping scow, the authorities only laughed at him, and referred him to general weyler, who happened at that time to be absent with an expedition to the interior. this was gratifying information, as it afforded an excuse for remaining in havana harbour until he should return.
in the meantime the mermaid, having sunk out of sight on the approach of danger, had found safe refuge under the stern of a spanish man-of-war that was moored close at hand. here she received a supply of fresh air through a flexible tube, one end of which was supported on the surface of the water by a small float. during the time that her occupants were thus compelled to remain in hiding, they amused themselves by so wedging the rudder of the warship as to render it immovable.
with the earliest twilight of that evening they returned to the tug and held a short consultation with her captain, who had used his eyes to such good purpose while on shore that he was enabled to direct them to a place from which he believed they could gain the city streets. this was most important, for though in the darkness they might have landed anywhere along the quay, they would still have been shut off from the streets by a tall and stout iron fence, the gates of which were always guarded, and at sunset locked for the night. this is in accordance with a regulation that not only forbids any vessel to enter or leave the port of havana between sunset and sunrise, but also prohibits all communication between the city and its harbour during the night.
the place indicated by the captain was a dock in which lay a number of fishing craft, and the entrance to which was closed by iron gates. as it was not likely that these extended very far below the surface, it was possible that the mermaid might pass beneath them. this proved to be the case; for when, after a long search and several narrow escapes from discovery, the dock was reached, the mermaid managed to squeeze under the barrier, and when she next rose to the surface she was inside the city lines. here she remained with her deck just awash, and in charge of the professor, while the two lads, filled with hopeful excitement, set forth in search of information that should guide their future action.
