is something awfully queer about this," he told himself. "I'll
go aboard."

He laid hands on the aeroplane and scrambled aboard. Quickly he sprang
to his feet, ready to tackle any foe that might have seen him crawl
aboard. Nothing happened.

Jack made a careful inspection of the disabled plane. Then, as he still
gazed around, a sudden thought struck him. Without taking time to
consider it, he sprang suddenly to the side of the plane and leaped
into the water and with swift and powerful strokes struck out for his
own craft.

Jack had hit upon the solution of the desertion of the German
aeroplane.

Even as Jack had lowered himself from the hydroplane and swam across
the water, the Germans in the other craft had done the same thing. Both
sides had struck the same plan almost simultaneously. Jack, in making a
wide detour as he approached the foes' machine, must have passed the
two Germans in the water.

Now, realizing that the Germans must be close to the hydroplane, had
they not already reached it, and remembering that Frank was wounded,
Jack felt a sudden dread steal over him. His long, powerful strokes
sent him through the water at great speed.

But the Germans had not made their presence known to Frank yet. Neither
was as swift a swimmer as Jack, and for that reason, their progress
through the water had been considerably slower. Also they had gone very
cautiously.

A short distance from the hydroplane, one had swum to one side of the
plane and the second to the other. The Germans also had discarded their
revolvers, for they had realized they would be useless after their
trip through the water. Also, not being expert swimmers, they had
wanted to be unhampered by weight as much as possible.

Frank was still guiding the plane about occasionally to avoid a chance
bullet from the enemy, but at the moment the Germans came close, he had
stopped the craft and was peering into the darkness, straining his ears
for the sound of a struggle that would tell him Jack was engaged with
the enemy.

Suddenly a sound came to his ears from across the water, but it was not
what he expected, although it was in Jack's voice:

"Frank! Look out! They are after you!"

Instantly, the lad understood the situation. He drew his revolver with
his uninjured arm and sprang to one side of the aeroplane. As he did
so, a figure reached up and grabbed him by the hand so that he could
not fire. At the same time a second figure clambered aboar