“Then where can he be?”

The inventor and the boy aviator stared at each other for an instant.

“Good gracious, this looks serious, indeed,” exclaimed Dr. Perkins; “not in his room, and not in the hotel, apparently. Where can he have gone to?”

“That’s what’s worrying me,” cried Harry, in a rather quavering tone; “I’m sure, perfectly sure, that that rascal Duval knows something about him wherever he is. Maybe he heard some word of a plot to injure the Sea Eagle and has gone down to see if he can frustrate it. Duval——”

“Yes; but Duval, if it is he, is not alone in this thing. Plumbo says there were two men and a lad.”

“Two men and a lad,” cried Harry joyously, “then the lad must have been Frank.”

“But who could the others have been? They all came together and sent our watchman away.”

“It’s all a deep mystery, doctor. I think our best plan is to make all the speed we can to the wharf. Perhaps we can find some solution there.”

“Yes; let us do so at once. I am all ready, are you?”

“Yes; I hurried to get dressed as soon as I heard the noise in the corridor.”