"At the risk of seeming rude, Mademoiselle, I am not going to be prying enough to make any guesses about your affairs," Captain Benson answered, quickly.

He thought he had gotten out of the matter as cleverly as it could be done.

"Some one is taking altogether too great an interest in my affairs, my Captain. I trust you have no hand in it, for it is possible that interference with my comfort will prove dangerous to the offenders.

Yet, pardon me, for I am sure that you, my Captain, would not cause me any uneasiness. Let those who do beware!"

As she let go of his arm and turned to go inside, Mlle. Nadiboff's smile was bright, almost friendly. Yet back of that smile, in her expressive eyes, lurked a look that made the boy start.

It was a look that spoke of deadly, things, and Captain Jack Benson had come quite to believe that Mlle. Nadiboff could be not only quite deadly at need, but also equally reckless.

CHAPTER XXI

A FRENCH RAT IN THE CORNER

As Mr. Farnum came around a bend in the veranda Jack hurried to him, handing over the letters. Then he related the little scene he had just witnessed in the office, and described how Mlle. Nadiboff had walked out with him.

"So the little minx was hinting at more mischief to come, was she?"

demanded the shipbuilder. "Jack, I believe she's equal to it. Her crowd are anyway, if it's true that Gaston, from his cell in jail, could plan the attempt to blow the 'Benson' last night."

Hal, too, soon came up and heard. He turned anxious gaze upon his chum.

"Jack, old fellow," he pleaded, "I know you're not much given to being afraid of things. But, at least, look out for yourself a bit. Be more prudent than you usually are about yourself. That crowd of foreign spies, having failed and having brought themselves into trouble, mean to have revenge. Any of us are liable, but you'll be the shining mark of all to be picked out."

"There can't be many more of that crowd left at large," laughed Jack, lightly.

"I wonder why the Secret Service men don't arrest Lemaire and the Nadiboff young woman?" asked Mr. Pollard, the last to rejoin the little group.

"Trotter and Packwood must have some good reasons of their own," Jack replied, thoughtfully. "For one thing, they hardly have any evidence that they could use against the pair."

"They could at least drive them from Spruce Beach," retorted the inventor.

"Perhaps the Secret Service man are giving the pair enough rope for their hanging," proposed Jack.

At that moment the two detectives were espied going past in a buggy.

They waved their hands to the party. Jack replied by a signal to halt.

He and Hal ran down to the road to speak to the detectives.

"If it's a fair question to ask," demanded Hal, "what are you going to do with Lemaire and Mlle. Nadiboff?"

"To tell you the truth, we don't know," Trotter answered. "We haven't anything we could very well fasten on them. But of this you may be sure; our various moves are known to them, and they're on the tenterhooks of anxiety wondering what's going to break loose next. More than that, both are sharp enough to have guessed that it would be impossible for either of them to get away from Spruce Beach, now, without our leave. But we'll have to leave you, now, boys. You've been of so much help to us that I don't mind telling you what we're up to at this moment. We're driving back to jail, and we're going to try to put the screws on Leroux and his Greek companion. If we can make 'em think we've gained new evidence against 'em, they may get scared and begin to talk. If they talk fast enough, they'll begin to tell some truth."

The buggy rolled along again.

"You didn't tell them a word about Mlle. Nadiboff's threats to you,"

muttered Hal.

"I didn't mean to," Jack replied, simply.

"Why not?"

"Well, for one thing, I couldn't swear that she did threaten me. She may have meant it all for nonsense."

"Yes," mocked Hal Hastings. "That, would be just like her!"

The submarine not being due to go out that day, the chums decided to remain on sh.o.r.e, in order to keep in touch with the march of events.

The day was so balmy that Mr. Farnum dropped into a chair on the porch, Pollard occupying the chair next to him. Hal, buying a magazine at the hotel news stand, sat on the edge of the porch, his feet touching the ground. Jack, his mind too full of problems to permit him to read, paced up and down the grounds. Finally he strolled, out past the gate, crossed the road and began to stroll along the shingle of bench.

Jacob Farnum removed his cigar from between his lips long enough to remark:

"As long as the lad keeps in sight, Pollard, it will be worth our while to keep an occasional eye on him."

"And when he goes out of sight--? asked the inventor, slowly.

"It will be high time to call him back. Somehow, Dave, I'm growing uneasy over the boy. I can't help the feeling that he's running into a good deal of danger that's likely to explode under him at any moment, just as that mine was intended to last night."

"It makes one feel uncanny to be at Spruce Beach," growled the inventor, savagely.

"Well, we can't run away," retorted Jacob Farnum, blandly.

"Why not, if we feel like it?"

The shipbuilder laughed.

"Why, Dave, a spirited lad like Jack Benson would be furious over anything that looked like a retreat. He'd be savage. Now, Dave, we can hardly afford to put such a slight on the boy who has had so much to do with our success."

"I suppose not," grunted Mr. Pollard, settling back in his chair.

"The odd part of it," said Farnum, presently, "is, that while we're the center of an international cyclone, so to speak, the rest of the folks at Spruce Beach don't know a word about it. Look at the crowds of folks around us who haven't even a breath of an idea of what has happened, or is, likely to happen. Not a soul around here, except our own few, have any idea that an attempt was made, last night, to blow up that mysterious-looking little submarine craft riding at her moorings out yonder."

"I wonder what the crowd would do, if it did know?" asked Pollard, gazing out curiously over the throngs of pleasure-seekers. "That shows what a dreamer you are, Dave, and how little you know of your own fellow citizens. What would the crowd do? Why, it would change itself into a mob. Mlle. Nadiboff would be hustled off out of town, Lemaire would be lynched, or mighty close to it, and it would be strange if the mob didn't march on the jail itself."

"Then it would never do to let the crowd know all that's happening, would it?" asked Pollard.

Jack, from thinking over the problems that had come up in connection with the spies, had at last let his attention wander to the crowds.

Down at the beach hundreds were taking an afternoon dip. Other hundreds were strolling up and down the sands. Children were building sand castles or houses. A good many small boats were out with pleasure parties. Yet many, both grown-ups and children, looked positively bored. They needed excitement.

"How near this crowd came to having something to talk about," muttered young Benson to himself, with a smile. "If that mine had gone off last night, no one at Spruce Beach would have felt dull to-day."

Finding that the afternoon air was making him dull and inclined to gape, Captain Jack turned back from the beach. He sauntered along the road, and was about to cross it, when he heard a sharp snap. It was like a subdued shot.

In the same instant a hissing sound went _pseu_! in front of his face.

A distinct breeze, small though it was, fanned his eyes. Then chug!

Something landed in the trunk of the tree he was pa.s.sing.