I must, on no account, afford ground for the suspicion that there was any connivance between the commander of the _Sword_ and me. For aught I know, Engineer Serko may have reason to be very skeptical about the discovery of the tunnel being accidental.

What, however, I am most concerned about is that the unlooked-for occasion to recover my liberty was lost. Shall I ever be afforded another chance? However this may be, my notice reached the English authorities of the archipelago, and they now know where Ker Karraje is to be found. When it is seen that the _Sword_ does not return to Bermuda, there can be no doubt that another attempt will be made to get inside Back Cup, in which, had it not been for the inopportune return of the tug, I should no longer be a prisoner.

I have resumed my usual existence, and having allayed all mistrust, am permitted to wander freely about the cavern, as usual.

It is patent that the adventure has had no ill effect upon Thomas Roch. Intelligent nursing brought him around, as it did me. In full possession of his mental faculties he has returned to work, and spends the entire day in his laboratory.

The _Ebba_ brought back from her last trip bales, boxes, and a quantity of objects of varied origin, and I conclude that a number of ships must have been pillaged during this marauding expedition.

The work on the trestles for Roch's engine goes steadily forward, and there are now no fewer than fifty engines. If Ker Karraje and Engineer Serko are under the necessity of defending Back Cup, three or four will be sufficient to render the island unapproachable, as they will cover a zone which no vessel could enter without being blown to pieces. And it occurs to me that they intend to put Back Cup in a state of defence after having argued as follows:

"If the appearance of the _Sword_ in the lagoon was due to chance the situation remains unchanged, and no power, not even England, will think of seeking for the _Sword_ inside the cavern. If, on the other hand, as the result of an incomprehensible revelation, it has been learned that Back Cup is become the retreat of Ker Karraje, if the expedition of the _Sword_ was a first effort against the island, another of a different kind--either a bombardment from a distance, or an attack by a landing party--is to be expected. Therefore, ere we can quit Back Cup and carry away our plunder, we shall have to defend ourselves by means of Roch's fulgurator."

In my opinion the rascals must have gone on to reason still further in this wise:

"Is there any connection between the disclosure of our secret--if it was, and however it may have been made--and the double abduction from Healthful House? Is it known that Thomas Roch and his keeper are confined in Back Cup? Is it known that the abduction was effected in the interest of Ker Karraje? Have Americans, English, French, Germans, and Russians reason to fear that an attack in force against the island would be doomed to failure?"

Ker Karraje must know very well that these powers would not hesitate to attack him, however great the danger might be. The destruction of his lair is an urgent duty in the interest of public security and of humanity. After sweeping the West Pacific the pirate and his companions are infesting the West Atlantic, and must be wiped out at all costs.

In any case, it is imperative that the inhabitants of Back Cup should be on their guard. This fact is realized, and, from the day on which the _Sword_ was destroyed, strict watch has been kept. Thanks to the new passage, they are able to hide among the rocks without having recourse to the submarine tunnel to get there, and day and night a dozen sentries are posted about the island. The moment a ship appears in sight the fact is at once made known inside the cavern.

Nothing occurs for some days, and the latter succeed each other with dreadful monotony. The pirates, however, feel that Back Cup no longer enjoys its former security. Every moment an alarm from the sentries posted outside is expected.