(First Published in Planet Stories, Spring 1949)

The observation deck of the President Marcus, this early in the ship's arbitrary morning, was deserted except for two shapeless figures. One of them was dead.

The body was sprawled in the curve of the deck about midway between two of the entrance wells. It had arms and legs, if you looked closely enough at the limp tangle of garments; it had a gray beard and a purple face.

The other figure had neither limbs nor a face. It was black, and it looked more like a pile of mud than anything else: a five-foot lump of black mud, slightly flattened at either side, with a cluster of black, stumpy filaments at the top. It moved slightly, dropping the filaments a little toward the dead body; then it flowed away again, and the filaments pointed straight up, toward the stars.

Phil Horitz came up at the forward end of the deck. He let the levitor push him gently clear of the well then stepped over to the glassine and looked out at the tiny blue disk that was Earth. His back was to the body and its watcher. He struck a cigarette, inhaling deeply, then turned around.

He swore and threw his cigarette away, leaping forward at the same instant. He skidded to a halt in front of the corpse and fell to one knee beside it. "Dead," he said. "Oh, Lord."

He searched the body swiftly, and came up with a flat metal box, attached by a silver chain to the body's middle. He tried the lid; it opened easily. The box was empty.

Horitz sighed and lifted the dead man's chin. Under the grey beard was a deeply-indented red line that encircled the throat.

He stood up and pressed a button on his wrist transceiver. "Walsh," he said. "Sommers. Get up to the observation deck. Thomasson has been murdered."

A deep voice swore fervently in his ear. He didn't wait for it to finish. He made an adjustment on the transceiver and said, "Captain Tooker, please. This is Philip Horitz."

A querulous male voice spoke: "Yes, Horitz? What do you want?"

Horitz repeated his message, and added, "I'm bringing the body down to Thomasson's stateroom. Get the ship's doctor and meet me there."

Two figures exploded out of the levitor well a dozen yards away; one bulky and grey-haired, the other lean and young. They ran up to Horitz, panting. The bulky one, Walsh, was still swearing.

"I watched him like a baby," he protested. "He told me he was going to get up at nine this morning, so I set my watch for eight. Why the howling hell did he ''

"Save it," said Horitz. "He did. I'll take his head, Sommers, you take his feet. Walsh, think you can carry Oscar?"

"Listen, Phil," said Sommers abruptly, "are the Equations gone?"

"Yes," Horitz told him. "They're gone."

Walsh grunted and, stooping, wrapped his arms around the black thing. He lifted it without apparent effort. The stumpy tendrils waved down toward him, then stood upright again, ignoring him. The other two picked up the body of Thomasson, and all three walked back to the levitor well from which they had come.

Captain Tooker and the medical officer, Dr. Evans, met them at the door of the dead man's stateroom. Tooker was boiling over. "Do you call yourselves Security agents?" he shouted. "Three of you, to protect one man, and you couldn't do it. I'll raise hell about this, Horitz, see if I don't."

Horitz and Sommers put the body down on the bed, and Dr. Evans fell quietly to examining it. "We'll find the killer," said Horitz grimly, "or else any hell you can raise will be a sneeze in a gale of wind. You don't know the half of this yet."

"I know that a man has been murdered on my ship," said Tooker.

"A man!" said Sommers, staring at him. "A whole planet may have been murdered, unless we get the Equations back."

"What equations?" said Tooker. "What the devil are you talking about?"

"The Thomasson Equations," said Sommers, "are the answer to the problem of faster-than-light space travel. Prof. Thomasson derived them from observations he made on the space shell this thing--" he gestured at Oscar--"landed on Pluto in, last year."

Captain Tooker glanced at Oscar with evident dislike. "Well," he said, "what are you going to do about it?"

"Have the ship searched," said Horitz quietly; "but that won't do any good. There are a hundred ways the killer could hide the Equations so that no search would ever find them. Our one chance, I'm afraid, is to get the only witness to tell us who garroted Thomasson."

"The witness?" said the captain, staring. "Who?"

Horitz turned to look at the black, five-foot lump, with its gently waving tendrils. "Oscar," he said.