fell just a few feet short. The third one landed on the
after-part of the stranger's deck-house.

And now there went fluttering up the top of the destroyer's mast the
international code signal:

"Stop or we'll sink you!"

It took another shell, this one crashing through the stern of the
stranger, to convince her skipper that the destroyer was in deadly
earnest.

By this time the "Grigsby" was a bare half-mile away, and going fast.

"We're bringing to bear on you to blow you out of the water," Darrin
signalled this time. "Will you stop?"

If he had made any plan to die fighting the fleeing skipper must have
lost his nerve at that point, for he suddenly swung his bow around,
reduced speed and moved ahead at mere steerage-way.

"Call Ensign Peters to clear away a launch with an armed crew," Darrin
directed. "I will accompany him, for I must see what reason that craft
had for firing on a British dirigible."

On either bow of the strange steamship was painted the national flag of
the same neutral nation to which the "Olga" had appeared to belong. She
flew no bunting.

"Stand by to receive boarding party," a signalman on the "Grigsby's"
bridge wigwagged as the launch started toward the water.

The two craft lay now not more than five hundred yards apart. Across the
water sped the fast power launch and came up alongside of the unknown
steamship, which displayed no name.

Not a human being was now visible on her deck. An undersized watch
officer had appeared on the bridge, but he now vanished.

"Who commands that destroyer?" demanded a voice in English, though it had
the broken accent of a German-born speaker.

"I do," Darrin replied.

"Then stay where you are, for you're covered!" ordered the same voice in
a frenzied tone. "We're not going to have you aboard. Signal the
destroyer to make off at top speed and we'll leave you when she is out of
sight. Refuse, and we kill you at once. Refuse, and you lose your life."

"Lower your gangway, and stop your nonsense," Dave ordered, angrily.
"You're dealing with the United States Navy, and your orders cannot
control our conduct."

"Then you are a dead man, at once!" declared the voice of the unseen
speaker.

Unnoticed by others, Darrin had given a hand signal to a petty officer in
the bow of the launch.

"If you do not lower your side gangway at once, we shall find our own
means for boarding," Dave shouted, wrathfully. "Instantly, sir!"

Thereupon half a dozen