"Look out! Don't shoot!" warned a voice sharply. It was Elaine. Her keen eyes and quick perception had recognized Arnold, leading Woodward.

We lowered our guns.

"Did you see a man, masked, come out here?" cried Woodward.

"No--he must have gone your way," we called.

"No, he couldn't."

Arnold was eagerly questioning the captain as Elaine and I approached.

"Dropped into the water--risked almost certain death," he muttered, half turning and seeing us.

"I want to congratulate you on your nerve for going in there," began Elaine, advancing toward the professor.

Apparently he neither heard nor saw us, for he turned as soon as he had finished with Price and went into the cave as though he were too busy to pay any attention to anything else.

Elaine looked up at me, in blank astonishment.

"What an impolite man," she murmured, gazing at the figure all stooped over as it disappeared in the darkness of the tunnel.

CHAPTER XII

THE DEATH CLOUD

Off a lonely wharf in a deserted part of the coast some miles from the promontory which afforded Del Mar his secret submarine harbor, a ship was riding at anchor.

On the wharf a group of men, husky lascars, were straining their eyes at the mysterious craft.

"Here she comes," muttered one of the men, "at last."

From the ship a large yawl had put out. As she approached the wharf it could be seen that she was loaded to the gunwales with cases and boxes.

She drew up close to the wharf and the men fell to unloading her, lifting up the boxes as though they were weighted with feathers instead of metal and explosives.

Down the sh.o.r.e, at the same time, behind a huge rock, crouched a rough looking tramp. His interest in the yawl and its cargo was even keener than that of the lascars.

"Supplies," he muttered, moving back cautiously and up the bluff. "I wonder where they are taking them?"

Marcus Del Mar had chosen an old and ruined hotel not far from the sh.o.r.e as his storehouse and a.r.s.enal. Already he was there, pacing up and down the rotted veranda which shook under his weight.

"Come, hurry up," he called impatiently as the first of the men carrying a huge box on his back made his appearance up the hill.

One after another they trooped in and Del Mar led them to the hotel, unlocking the door.

Inside, the old hostelry was quite as ramshackle as outside. What had once been the dining-room now held nothing but a long, rickety table and several chairs.

"Put them there," ordered Del Mar, directing the disposal of the cases.

"Then you can begin work. I shall be back soon."

He went out and as he did so, two men seized guns from a corner near-by and followed him. On the veranda he paused and turned to the men.

"If any one approaches the house--any one, you understand--make him a prisoner and send for me," he ordered. "If he resists, shoot."

"Yes, sir," they replied, moving over and stationing themselves one at each angle of the narrow paths that ran before the old house.

Del Mar turned and plunged deliberately into the bushes, as if for a cross country walk, un.o.bserved.

Meanwhile, by another path up the bluff, the tramp had made his way parallel to the line taken by the men. He paused at the top of the bluff where some bushes overhung and parted them.

"Their headquarters," he remarked to himself, under his breath.

Elaine, Aunt Josephine and I were on the lawn that forenoon when a groom in resplendent livery came up to us.

"Miss Elaine Dodge?" he bowed.

Elaine took the note he offered and he departed with another bow.

"Oh, isn't that delightful," she cried with pleasure, handing the note to me.

I read it: "The Wilkeshire Country Club will be honored if Miss Dodge and her friends will join the paper chase this afternoon. L.H. Brown, Secretary."

"I suppose a preparation for the fox or drag hunting season?" I queried.

"Yes," she replied. "Will you go?"

"I don't ride very well," I answered, "but I'll go."

"Oh, and here's Mr. Del Mar," she added, turning. "You'll join us at the Wilkeshire hunt in a paper chase this afternoon, surely, Mr. Del Mar?"

"Charmed, I'm sure," he agreed gracefully.

For several minutes we chatted, planning, then he withdrew. "I shall meet you on the way to the Club," he promised.

It was not long before Elaine was ready, and from the stable a groom led three of the best trained cross-country horses in the neighborhood, for old Taylor Dodge, Elaine's father, had been pa.s.sionately fond of hunting, as had been both Elaine and Aunt Josephine.

We met on the porch and a few minutes later mounted and cantered away.

On the road Del Mar joined us and we galloped along to the Hunt Club, careful, however, to save the horses as much as possible for the dash over the fields.

For some time the uncouth tramp continued gazing fixedly out of the bushes at the deserted hotel.

Suddenly, he heard a noise and dropped flat on the ground, looking keenly about. Through the trees he could see one of Del Mar's men stationed on sentry duty. He was leaning against a tree, on the alert.

The tramp rose cautiously and moved off in another direction to that in which he had been making his way, endeavoring to flank the sentry.

Further along, however, another of Del Mar's men was standing in the same attentive manner near a path that led from the woods.