“You must catch him,” she appealed.  “Father’s life is in danger.  Oh, you simply must.”

I knew Captain Marlowe to be a proverbial fire-eater, but in this case, at least, he was no alarmist.  For, on the table, as he spoke, he laid a real bullet.

Marjorie Marlowe shuddered at the mere sight of it and glanced apprehensively at him as if to reassure herself.  She was a tall, slender girl, scarcely out of her teens, whose face was one of those quite as striking for its character as its beauty.  The death of her mother a few years before had placed on her much of the responsibility of the captain’s household and with it a charm added to youth.

More under the spell of her plea than even Marlowe’s vigorous urging, Kennedy, without a word, picked up the bullet and examined it.  It was one of the modern spitzer type, quite short, conical in shape, tapering gradually, with the center of gravity back near the base.

“I suppose you know,” went on the captain, eagerly, “that our company is getting ready to-morrow to launch the Usona, the largest liner that has ever been built on this side of the water—­ the name is made up of the initials of the United States of North America.

“Just now,” he added, enthusiastically, “is what I call the golden opportunity for American shipping.  While England and Germany are crippled, it’s our chance to put the American flag on the sea as it was in the old days, and we’re going to do it.  Why, the shipyards of my company are worked beyond their capacity now.”

Somehow the captain’s enthusiasm was contagious.  I could see that his daughter felt it, that she was full of fire over the idea.  But at the same time something vastly more personal weighed on her mind.

“But, father,” she interrupted, anxiously, “tell them about the bullet.”

The captain smiled indulgently as though he would say that he was a tough old bird to wing.  It was only a mask to hide the fighting spirit underneath.

“We’ve had nothing but trouble ever since we laid the keel of that ship,” he continued, pugnaciously, “strikes, a fire in the yard, delays, about everything that could happen.  Lately we’ve noticed a motor-boat hanging about the river-front of the yards.  So I’ve had a boat of my own patrolling the river.”

“What sort of craft is this other?” inquired Kennedy, interested at once.

“A very fast one—­like those express cruisers that we hear so much about now.”

“Whose is it?  Who was in it?  Have you any idea?”

Marlowe shook his head doubtfully.  “No idea.  I don’t know who owns the boat or who runs it.  My men tell me they think they’ve seen a woman in it sometimes, though.  I’ve been trying to figure it out.  Why should it be hanging about?  It can’t be spying.  There isn’t any secrecy about the Usona.  Why is it?  It’s a mystery.”

“And the shot?” prompted Craig, tapping the bullet.