It was agreed that the submarine would go as far as Dunkirk, in the hope that opportunity would there present itself for the passengers to pursue the returning course in some other vessel.
A surprise beyond any dream of great fortune awaited them at Dunkirk.
This port just then was a working out point for aircraft for scout duty on the North Sea.
From the conning tower of the submarine Henri and Billy were watching with keen interest the aërial maneuvers then in progress. Suddenly the lighter machines were overshadowed by a flying shape that darted like an eagle among sparrows.
The long, tapering hull, and the float attachments, the trim, wicked gun in the bow, proclaimed this giant patrol of the air a fighting sea-plane.
With engines quiet, down dived the great steel-breasted bird; then a swift upturning and she shot level upon the water and rode the waves like a swan.
A stone could easily have been tossed from the bridge of the submarine upon the upper plane of the aircraft, so near together were they.
The pilot of the sea-plane turned to view the rival factor in modern warfare, half rising as he did so.
Mutual recognition flashed across the few separating yards of distance.
“Hello, captain!” shouted Billy.