He banged shut the door just as the hermit and the soldiers made a rush at him. On the door they battered. But it was in vain. The door was locked.

In the office Del Mar hastily went to a corner, after barring the door, and lifted a trap-door in the floor, known only to himself.

Elaine did not move or make any attempt to escape, for Del Mar in addition to having a vicious looking automatic in his hand kept a watchful eye on her.

Outside the office, the soldiers, led by the hermit and Woodward continued to batter at the door.

"Now--go down that stairway--ahead of me," ordered Del Mar.

Elaine obeyed tensely, and he followed into his emergency exit, closing the trap.

"Beat harder, men," urged the hermit, as the soldiers battered at the door.

They redoubled their efforts and the door bent and swayed.

At last it fell in under the sheer weight of the blows.

"By George--he's gone--with Elaine," cried the hermit, looking at the empty office.

Feverishly they hunted about for a means of escape but could find none.

"Pound the floor and walls with the b.u.t.ts of your guns," ordered Arnold. "There must be some place that is hollow."

They did so, going over all inch by inch.

Meanwhile, through the pa.s.sage, along a rocky stairway, Del Mar continued to drive Elaine before him, up and ever up to the level of the land.

At last Elaine, followed by Del Mar, emerged from the rocky pa.s.sage in a cleft in the cliffs, far above the promontory.

"Go on!" he ordered, forcing her to go ahead of him.

They came finally to a small hut on a cliff overlooking the real harbor.

"Enter!" demanded Del Mar.

Still meekly, she obeyed.

Del Mar seized her and before she knew it had her bound and gagged.

Down in the little office our men continued to search for the secret exit.

"Here's a place that gives an echo," shouted one of them.

As he found the secret trap and threw it open, the hermit stripped off the c.u.mbersome diving-suit and jumped in, followed by Woodward, myself and the soldiers.

Upward we climbed until at last we came to the opening. There we paused and looked about. Where was Del Mar? Where was Elaine? We could see no trace of them.

Finally, however, Arnold discovered the trail in the gra.s.s and we followed him, slowly picking up the tracks.

Knowing that the submarine would cruise about and wait for him, Del Mar decided to leave Elaine in the hut while he went out and searched for a boat in which to look for the submarine.

Coming out of the hut, he gazed about and moved off cautiously.

Stealthily he went down to the sh.o.r.e and there looked up and down intently.

A short distance away from him was a pier in the process of construction. Men were unloading spiles from a cable car that ran out on the pier on a little construction railway, as well as other material with which to fill in the pier. At the end of the dock lay a power-boat, moored, evidently belonging to some one interested in the work on the pier.

The workmen had just finished unloading a car full and were climbing back on the empty car, which looked as if it had once been a trolley.

As Del Mar looked over the scene of activity, he caught sight of the powerboat.

"Just what I want," he muttered to himself. "I must get Elaine. I can get away in that."

The workmen signalled to the engineer above and the car ran up the wharf and up an incline at the sh.o.r.e-end.

The moment the car disappeared, Del Mar hurried away in the direction he had come.

At the top of the grade, he noticed, was a donkey engine which operated the cable that drew the car up from the dock, and at the top of the incline was a huge pile of material.

The car had been drawn up to the top of the grade by this time. There the engineer who operated the engine stopped it.

Just then the whistle blew for the noon hour. The men quit work and went to get their dinner pails, while the engineer started to draw the fire. Beside the engine, he began to chop some wood, while the car was held at the top of the grade by the cable.

In our pursuit we came at last in sight of a lonely hut. Evidently that must be a rendezvous of Del Mar. But was he there? Was Elaine there? We must see first.

While we were looking about and debating what was the best thing to do, who should appear hurrying up the hill but Del Mar himself, going toward the hut.

As we caught sight of him, Arnold sprang forward. Woodward and I, followed by the soldiers also jumped out.

Del Mar turned and ran down the hill again with us after him, in full cry.

While we had been waiting, some of the soldiers had deployed down the hill and now, hearing our shouts, turned, and came up again.

Beside his engine, we could see an engineer chopping wood. He paused now in his chopping and was gazing out over the bay. Suddenly he had seen something out in the water that had attracted his attention and was staring at it. There it moved, nothing less than a half-submerged submarine.

As the engineer gazed off at it, Del Mar came up, unseen, behind him and stood there, also watching the submarine, fascinated.

Just then behind him Del Mar heard us pursuing. He looked about as we ran toward him and saw that we had formed a wide circle, with the men down the hill, that almost completely surrounded him. There was no chance for escape. It was hopeless.

But it was not Del Mar's nature to give up. He gave one last glance about. There was the trolley car that had been converted into a cable way. It offered just one chance in a thousand. Suddenly his face a.s.sumed an air of desperate determination.

He sprang toward the engineer and grappled with him, seeking to wrest the axe from his hand. Every second counted. Our circle was now narrowing down and closing in on him.

Del Mar managed to knock out the engineer, taken by surprise, just as our men fired a volley. In the struggle, Del Mar was unharmed. Instead he just managed to get the axe.

An instant later a leap landed him on the cable car. With a blow of the axe he cut the cable. The car began to move slowly down the hill on the grade.