Like the cries of birds, far away, came men’s voices from outside and down the tunnel.
“Hey, what goes on out there?” said Mac, bleak blue eyes beginning to take on a speculative look as they rested on Benson’s white, still face. “What are they sayin’?”
“They are saying,” said The Avenger calmly, “that they can’t get that steel door open to escape.”
“What?” gasped Smitty. Josh and Nellie and Rosabel stared with their mouths open.
“I set the outer bar in such a way that when I banged the door shut from the inside, the bar would fall and block the exit,” said Benson calmly. “I did that because from the nature of the trap and the layout of the blueprints, it was evident that our doom was to be death by drowning.”
“B-blueprints?” said Josh.
“In the Congressional Library.” The water was up to their knees, and spurting in around the dungeon door in flat sheets. “Blueprints of this abandoned traffic tunnel are there, naturally. I stopped on my way to have a look.”
“So you let the men and their precious leader, Fram, throw the lever that will drown them all like the rats they are!”
“I don’t take life, as you know,” was The Avenger’s calm, cold retort. “If murderers kill themselves in their efforts to kill us, that is their own affair. So I let them throw that lever, knowing that by the time they found the steel door locked against them they wouldn’t have time to get back and shut the floodgate again. By then, the rush of the water would have cut them off from it. But they had their chance. You heard me warn Fram not to do it.”
The cold, even voice was like something coming from a machine — a machine of vengeance — rather than a human being.
“But, Muster Benson,” spluttered the Scot. “Ye’ve killed us, too. We’ll be drowned along with the rats. Look at this, now!”
The water was up to their waists.
“What I saw in the blueprints at the Congressional Library,” said Benson, “governed my procedure here. This cell, the only logical place for prisoners in the tunnel length, is in a bend of the tunnel, and its roof is four feet above the roof of the tube outside. It is logical to assume that inrushing water will trap air in this cell.”
“So that’s why you stuffed the crack at the top of the door!” Josh said.
“Yes.” The Avenger’s tone was as even and unmoved as if they were all at a garden party speaking of the arrangements of flowers. “That was to keep the air in this cell from oozing out the top of the door as the water pressed in at the bottom. It’s impossible to caulk the door cracks to keep the water out. The pressure is too great. But it is possible to keep the air in.”
Smitty and Mac were silent. It all sounded very smooth and easy; but they knew that only a great engineer could have read this possibility in a glance at a blueprint.
And even a great engineer, in a case like this, might have miscalculated a very little.
In which case they would all die.
“The men outside?” shuddered Nan Stanton. The shiver was caused by the icy water as well as her fears. The water was now up to the dainty chin of Nellie, who was the shortest of them.
Benson didn’t answer. But they all knew the reply.
The men outside in the tunnel were drowned. Fram included. The tube was flooded from floor to roof, since no more rush of water sounded. And spurting into the cell around the door. It would soon be up to the ceiling in here. Unless Benson’s delicate calculations of elevation and curve was precisely right.
“It still seems fantastically impossible that Dr. Fram was the head of this,” said Nan. “You are sure, Mr. Benson?”
“Even without his presence here at the end, I would have known,” said The Avenger. Nellie was standing on tiptoe to keep her head above water. “The whole plot was one of applied psychology. Only a professional psychologist, trained in the knowledge of manipulation of minds, could have concocted it. Only a master of subtlety like Fram. Certainly it would have been beyond the powers of an ordinary businessman like Tetlow Adams.”
“But why?” burst out Nellie. “Fram wouldn’t want the helium in the park.”
“There was never a question of helium,” said Benson, watching the inrush of water as coldly and impersonally as if his life were not dependent on it. “Mac and Smitty reported seeing a deer and jackrabbit, at Lost Geyser, with incurable sores on their flanks. Don’t you really know what must have made those sores, Mac?”
The Scot, after a few seconds, emitted a kind of squawk at his own thick-headedness in not seeing it before. Particularly since he was one of the world’s finest pharmacists and an equally fine chemist.
“Radium!”
“Of course,” said Benson. The flood was coming into the cell more slowly. But it was still coming in. “Radium. That’s why Fram wanted to get the park — intending to force Adams to bid it in under his own mining corporation titles. There are evidently pitchblende deposits around Lost Geyser so rich, that animals lurking in the vicinity too long develop incurable radium burns. Such deposits are worth uncounted millions to the man who could acquire mineral rights to Bison Park.”
Nellie gasped aloud, then repressed the sound. She was forced to tread water, now. She couldn’t touch the floor any more.
The ceiling slowly neared them till it was only a foot above their heads, and they were all treading water.
The flood was coming in extremely slowly, as the air between water and roof became more and more compressed.
But it still had not entirely stopped!
Nan Stanton began to cry, first silently and then hysterically. All very well to trust The Avenger as blindly as these others seemed to be doing. But, after all, he was only mortal; even he could make a mistake. Besides, assuming there would remain enough air to keep them alive in here for a while — then what? There was at least a quarter of a mile of tunnel between them and the street exit, filled from floor to roof by water. How could they ever get out of that? And the door to this cell, of solid metal, was barred from the outside. How could they get that open?
The bulb in the ceiling was still burning. Rosabel paddled to Nan’s side and put an arm around her to comfort her. At that moment the light blinked out as water, far away, finally caused a short circuit somewhere in the line.
There was about six inches between water and ceiling.
“All of you,” came The Avenger’s calm voice, “go to the walls. They are rough, unfinished cement. You can find irregularities to cling to, so that you won’t tire yourselves treading water constantly.”
They did as commanded and clung with fingertips to irregularities, with their faces tilted so that nostrils and mouths were in the thin stratum of air.
And then the flow had stopped. Benson had calculated the air pocket in the cell, in advance, to the inch.
“Pressure is equalized,” his calm voice came. “We’ll leave now.”
Nan Stanton couldn’t guess what he meant. But his aides knew.
He had his small combination gas mask and oxygen dispenser under the lining of his coat. He clipped that onto his nostrils and over his mouth; then he sank on the floor of the cell, taking in oxygen from a rubber bladder as he did so.
Also with him, as usual, was one of Mac’s inventions. A tiny blowtorch whose fuel was several pellets which, when crushed and moistened, produced a blue, terrifically hot point of flame.
It would work under water as well as in air.
They could all see the blue point move slowly in a circle, under the water, as Benson cut a hole in the steel door. Then a little wavering of the water told of the door being partly opened.
Benson’s head came above surface again.