Yet, some of the time, they remained near the entrance to the ballroom.  It was here that M. Lemaire, in evening clothes, saw them and bowed most amiably.

“You do not care for the gaiety of the dance?” he inquired.

“No,” replied Jacob Farnum, evasively.  “We are looking for Captain Benson, and thought it just possible he had entered the ballroom.”

“Did he not tell you, this afternoon, whether he would be at the dance?” Lemaire inquired, in a tone of polite curiosity only.

“We didn’t see him this afternoon,” replied Mr. Farnum, rather curtly.

“You astonish me,” cried the Frenchman.

“In fact we have not seen Captain Benson since we left him on an automobile ride this morning.”

“Ah!  I had not heard of that,” murmured the Frenchman.  “I trust nothing is wrong with the gallant young fellow.”

“Oh, that’s hardly likely,” drawled Jacob Farnum, with an effort.  “Captain Jack Benson a lad with a pretty good idea of how to take care of himself.”

While speaking Farnum did not look particularly at the Frenchman, but trusted to the boys to watch the man’s face covertly.  M. Lemaire, however, proved to be a good actor and a master of facial expression.

As soon as he could, without attracting attention, Jacob Farnum drew his little force to one side.

“Something serious has happened to Jack,” muttered the shipbuilder, moodily.  “It may have been an accident, but I believe it’s ten times more likely that that infernal gang of spies have trapped the lad and brought harm to him.  We’ve got to act, and act fast!”

CHAPTER XII

IN THE POWER OF THE SPIES

Something had, indeed, “happened” to Jack Benson, and much more was likely to happen.

The young submarine captain lay on a pile of dried grass that had been thrown on a board floor.  His hands were still manacled.  Worse, one of his feet now had an ankle-ring fastened securely, and this was chained to a stout staple driven in the floor.

It was a curious place in which young Benson lay, a place with a strange history.

Years before a tunnel had been bored into the side of a hill.  After the tunnel had been lined with a masonry of stone it was not more than three feet in diameter.  This tunnel led into an artificial cave some eighteen feet square and nine feet high.  This cave had been shored up and boarded as to ceiling, floor and walls.

A great deal of labor had been expended in building this curious place under a low hill.  Yet the original builders had figured that their time so spent would yield large returns.  This part of the Florida coast lay conveniently near to Cuba.  On moonless nights a small sailing craft would put in along the coast, laden with smuggled Havana cigars.  There being no safe place along the shore in which to store the cigars, this place, hidden well in a forest, had been constructed as a safe depository.  For some time the cigar smugglers had prospered.  Then, as was to have been expected, Uncle Sam’s sharp eyed customs men ran the illegal business down, arresting the smugglers, all of whom were subsequently imprisoned.