Take the hydroplane aft and fly south.

Because, of course, my first thought was that it must have been Percy Carberry's work; but now that you tell me he was here, and knew we hadn't fetched our hydroplane home, I hardly know what to think.

"Hullo," he added hastily the next moment; "what's that?" He pointed toward the island, and the occupants of the homing hydroplane saw, slowly rising from it in the still air, four straight columns of blue smoke.