The wheel was dish-shaped, as all roulette wheels are. In its rounded bottom were numbered slots, where the little ivory ball was to end its journey and proclaim gambler's luck.

But the little ball was not in one of the bottom slots!

The tiny ivory sphere was half up the rounded side of the wheel, like a pea clinging alone high up on the slant of a dish!

An exclamation came from Keane's lips. He stared at the ball. What in heaven's name kept it from rolling down the steep slant and into the rounded bottom? Why would a sphere stay on a slant? It was as if a bowl of water had been tilted--and the water's surface had taken and retained the tilt of the vessel it was in instead of remaining level!

He lifted the ball from the sloping side of the wheel. It came away freely, but with an almost intangible resistance, as if an unseen rubber band held it. When he released it, it went back to the slope. He rolled it down to the bottom of the wheel. Released, it rolled back up to its former position, like water running up-hill.

Keane felt a chill touch him. The laws of physics broken! A ball clinging to a slant instead of rolling down it! What dark secret of nature had Doctor Satan mastered now?

But the query was not entirely unanswered in his mind. Already he was getting a vague hint of it. And a little later the hint was broadened.

The phone rang. He answered it.

"Mr. Keane? This is Doctor Grays. The autopsy on Wilson has been begun, and already a queer thing has been disclosed. It's about his heart."

"Yes," said Keane, gripping the phone.

"His heart is ruptured in a hundred places--as though a little bomb had exploded in it! Don't ask me why, because I can't even give a theory.

It's unique in medical history."

"I won't ask you why," Keane said slowly. "I think--in a little while--I'll tell you why."

He hung up and strode toward the door. But at the roulette table he paused and stared at the wheel with his gray eyes icily blazing.

_It seemed to him the wheel had moved a little!_

He had unconsciously lined up the weirdly clinging ball with the k.n.o.b on the outer door, as he examined it awhile ago. Now, as he stood in the same place, the ball was not quite in that line. As if the wheel had rotated a fraction of an inch!

"Yes, I think that's it," he whispered, with his face a little paler than usual.

And a little later the words changed in his brain to: "I _know_ that's it. A fiend's genius.... This is the most dangerous thing Doctor Satan has yet mastered!"

He was talking on the phone to the jeweler to whom Weems' watch had been sent.

"What did you do to that watch?" the jeweler was saying irritably.

"Why?" parried Keane.

"There doesn't seem to be anything wrong with it. And yet it simply won't go. And I can't make it go."

"There's nothing wrong with it at all?"

"As far as I can find out--no."

Keane hung up. He had been studying for the dozenth time the demand note Doctor Satan had written the officials:

"Gentlemen of the Blue Bay Development: This is to request that you pay me the sum of one million, eight hundred and two thousand, five hundred and forty dollars and forty-eight cents at a time and place to be specified later. As a sample of what will happen if you disregard this note, I shall strike at one of your guests, Mathew Weems, within a few minutes after you read this. I guarantee that disaster and horror shall be the chief, though uninvited, guests at your opening unless you comply with my request. Mathew Weems shall be only the first if you do not signify by one a. m. whether or not you will meet my demand. DOCTOR SATAN."

Keane gave the note back to Blue Bay's police chief, who fumbled uncertainly with it for a moment and then stuck it in his pocket.

Normally a competent man, he was completely out of his depth here.

One man with a heart that seemed to have been exploded internally; ten people who were dead, yet lived, and who stood or sat like frozen statues....

He looked pleadingly at Ascott Keane, whom he had never heard of but who wore authority and competence like a mantle. But Keane said nothing to him.

"An odd extortion amount," he said to Gest. "One million, eight hundred and two thousand, five hundred and forty dollars and forty-eight cents!

Why not an even figure?"

He was talking more to himself than to the president of Blue Bay. But Gest answered readily.

"That happens to be the precise sum of the cash reserve of Blue Bay Development."

Keane glanced at him sharply. "Is your financial statement made public?"

Gest shook his head. "It's strictly confidential. Only the bank, and ourselves, know that cash reserve figure. I can't imagine how this crook who signs himself Doctor Satan found it out."

_4. The Sh.e.l.l_

The house was serene and beautiful on the bay sh.o.r.e. The sun beat back from its white walls, and glanced in at the windows of the rear terrace.

It shone on a grotesque figure there; a man with the torso of a giant, but with no legs--a figure that hitched itself along on the backs of calloused hands, using muscular arms as a means of locomotion.

But this figure was not as bizarre as the one to be found within the house, behind shades drawn to keep out any prying eyes.

Here, in a dim room identifiable as a library, a tall man stood beside a flat-topped desk. But all that could be told of the figure was that it was male. For it was cloaked from heels to head in a red mantle. The hands were covered by red rubber gloves. The face was concealed by a red mask, and over the head was drawn a red skull-cap with two small projections in mocking imitation of Lucifer's horns.

Doctor Satan!

In the red-gloved hands was a woman's gold-link purse. Doctor Satan opened it. From the purse he drew a thing that defied a.n.a.lysis and almost defied description.

It was of metal. It seemed to be a model in gleaming steel of a problem in solid geometry: it was an angular small cage, an inch wide by perhaps three and a half inches square. That is, at first it seemed square. But a closer look revealed that no two corresponding sides of the little cage were quite parallel. Each angle, each line was subtly different.

Doctor Satan pointed it at the library wall. The end he pointed was a trifle wider than the end heeled in the palm of his hand. On this wider end was one bar that was fastened only at one end. The red-covered fingers moved this bar experimentally, slowly, so that it formed a slightly altered angle with the sides....

The library wall was mist, then nothingness. The street outside was not a street. A barren plain stood there, strewn with rocky shale, like a landscape on the moon.

The little bar was moved back, and the library wall was once more in place. A chuckle came from the red-masked lips; a sound that would have made a hearer shiver a little. Then it changed to a snarl.

"Perfect! But again Ascott Keane interferes. This time I've got to succeed in removing him. An exploded heart...."

He put the mysterious small cage back in the gold-link purse, and opened the desk drawer. From it he took a business letterhead. It was a carbon copy, with figures on it.