"Are you sure, Captain?"

"No, sir. It's only a possibility, but a good one."

Hepton was making his rifle bark again, deep, snappy and angry in its throat, in answer to a challenge from sh.o.r.e, but Powell Seaton stood surveying the weather with a look of deepest concern.

Then he turned to regard the drab seventy-footer at anchor near by.

"It would be the enemy's real chance, wouldn't it?" he inquired.

"Just what I dread, sir," Captain Tom admitted. "Let us be wrapped in a thick bank of fog, and the Drab would be out of our vision and hearing in a very short time."

"Shades of hard luck!" groaned the charter-man, growing pallid.

Off on the seaward horizon an indefinite haze was soon observable. To the untrained eye it didn't look like much. Though Mr. Seaton spoke of it, he didn't appear much concerned.

"It'll be a pity to bother him until the time comes when he throbs with worry," thought Captain Tom Halstead, sympathetically. "But if that low-hanging haze doesn't spell t-r-o-u-b-l-e, then I've been raised among a different breed of sea fogs!"

The crashing of sparks over the spark-gap had ceased for the present, and Joe, reporting that there was no wireless craft within reach of his limited aerials, was on deck once more, waiting until the time should come around for another trial.

Hank had gone below to start the motors, connecting them with the dynamo, to renew the supply of electrical "juice" in the storage batteries, which was running low, as proved by the last message sent.

The chug-chug of the twin motors was heard over on the seventy-footer, and soon an unknown man, his cap pulled well down over his eyes, appeared at the stern of the Drab. He took a long, keen look at the "Restless."

"He's wondering if we're going to hoist the mud-hook," smiled Tom.

"And hoping that we are," grinned Joe. "Oh, but we must be an eyesore to those wistful scoundrels!"

Powell Seaton now spent most of his time gazing at the line of haze, which, by degrees, was growing bigger and coming nearer.

"Captain Halstead," he faltered, "I'm beginning to feel certain that you're a prophet."

"Or a Jonah?" laughed Tom, though it was not a very cheerful sort of laugh.

"No, no, no!" cried the charter-man, earnestly. "Never that! The little luck that I've had in these trying days has all come through you youngsters. Without you I'd have been flat on my back in the fearful game that I'm playing with such desperate hopefulness against hope. But I see our fog is coming in as a sure thing. If it envelops us, what can you do with regard to that drab-tinted sea-monster over yonder?"

"It depends upon the depth and duration of the fog, sir," Halstead answered. "We have our motors going. At the first strong sign of our getting hemmed in by it we'll lift our mud-hook [the anchor] and move in closer. If the fog isn't too thick we may be able to take up a position where we can at least observe her dimly. If she starts to pull out into a fog-bank, we'll follow at her heels, keeping as close as necessary to keep the Drab's stern flag-pole in sight. We won't lose her if there's any way of stopping it."

The advance guard of the fog was in upon them by the time that Joe went once more to his sending table in the forward end of the cabin.

The light mist extended to the sh.o.r.e, though it did not altogether screen it. But the lookout on the Drab's deck appeared wholly watchful at the weather side of the craft.

"Not in touch with any other wireless boat yet," reported Dawson, coming on deck, presently.

"Look at that heavier white curtain rolling in," uttered Powell Seaton, in a tone near to anguish.

Whoever was in the drab boat's pilot house took occasion to toot derisively twice on the auto whistle.

"That's as much as warning us that their turn is coming," declared Mr.

Seaton, wrathfully.

Their faces were wet, now, with the fog as it rolled in. Slowly the nearby sh.o.r.e faded, wrapped in the mist.

"We'd better get up anchor," decided Skipper Tom. "Come along, Hank, and you, Hepton."

As the anchor came up and was stowed, Captain Halstead moved the deck speed control ever so little. The "Restless" began to barely move through the water. They overhauled the seventy-footer, pa.s.sing within a hundred feet of her starboard rail. Yet only the same deck watch appeared in sight. He favored those on the bridge deck of the "Restless" with a tantalizing grin.

Halstead slowly circled the drab seventy-footer, Mr. Seaton keeping ever a watchful eye on the stranger.

"There! They're hoisting anchor!" muttered the charter-man, at last.

"I saw 'em start," nodded the young skipper. "And the fog is growing thicker every minute."

"How are you going to beat them, if they try hard to get away?"

"I don't know," confessed Halstead, honestly. "We may keep 'em in trail, but the chances are all in favor of the drab boat."

Presently the seventy-footer slipped slowly away from her anchorage.

Halstead promptly closed in, keeping not more than a hundred feet behind her drab stern. If the fog grew no heavier, and the enemy's speed no greater, he could maintain his position.

But the sea-born fog continued to come, looking as though it arrived in ever-increasing billows.

Once the seventy-footer's stern vanished for a moment or two. Tom, cautiously increasing the speed, soon came in sight of that drab stern once more.

"I don't want to croak, sir," warned the young motor boat skipper, "but, luck aside, it looks as though we're about done for in this salt water blindman's buff."

"I realize it," nodded Powell Seaton.

Just then the seventy-footer crawled ahead again into the fog, and was lost to the pursuer. Throwing the wheel somewhat to port, Captain Halstead tried to come up on the Drab's quarter. A full minute's anxious suspense followed, but the enemy's stern did not show through the white shroud of the atmosphere.

Then Halstead threw off the power without applying the reverse. The "Restless" drifted under what was left of her headway.

"They've done it," uttered Tom Halstead, grimly. "They've given us the slip--gotten away in this white ma.s.s of mystery!"

Shaking, Powell Seaton leaned against the deck-house, his face pallid with sheer misery.

CHAPTER XVI

A GLEAM OF HOPE THROUGH THE SHROUD OF FOG

Resting one hand lightly on the top spokes of the wheel, young Halstead turned to his employer with a look of keenest sympathy.

"Is there any order you wish to give now, Mr. Seaton?"

"What order can I give," demanded the charter-man, with a piteous smile, "unless it be to say, 'find the drab boat'?"

Tom made a grimace.