SK540, the 27th son of two very ordinary white laboratory rats, surveyed his world.

He was no more able than any other rat to possess articulate speech, or to use his paws as hands. All he had was a brain which, relative to its size, was superior to any rat’s that had hitherto appeared on Earth. It was enough.

In the first week of gestation his embryo had been removed to a more suitable receptacle than the maternal womb, and his brain had been stimulated with orthedrin, maxiton and glutamic acid. It had been continuously irrigated with blood. One hemisphere had been activated far in excess of the other, since previous experiments had shown that increased lack of symmetry between the hemispheres produced superior mentality. The end-result was an enormous increase in brain-cells in both hemispheres. His brain showed also a marked increase in cholinesterase over that of other rats.

SK540, in other words, was a super-rat.

The same processes had been applied to all his brothers and sisters. Most of them had died. The few who did not, failed to show the desired results, or showed them in so lopsided and partial a manner that it was necessary to destroy them.

All of this, of course had been mere preparation and experimentation with a view to later developments in human subjects. What SK540’s gods had not anticipated was that they would produce a creature mentally the superior, not only of his fellow-rats, but also, in some respects, of themselves.

He was a super-rat: but he was still a rat. His world of dreams and aspirations was not human, but murine.

What would you do if you were a brilliant, moody young super-rat, caged in a laboratory?

SK540 did it.

What human beings desired was health, freedom, wealth, love, and power. So did SK540. But to him health was taken for granted; freedom was freedom from cages, traps, cats, and dogs; wealth meant shelter from cold and rain and plenty to eat; love meant a constant supply of available females.

But power! It was in his longing for power that he most revealingly displayed his status as super-rat.

Therefore, once he had learned how to open his cage, he was carefully selective of the companions--actually, the followers--whom he would release to join his midnight hegira from the laboratory. Only the meekest and most subservient of the males--intelligent but not too intelligent--and the most desirable and amiable of the females were invited.

Once free of the cages, SK540 had no difficulty in leading his troop out of the building. The door of the laboratory was locked, but a window was slightly open from the top. Rats can climb up or down.

Like a silver ribbon they flowed along the dark street, SK540, looking exactly like all the rest, at their head. Only one person in the deserted streets seems to have noticed them, and he did not understand the nature of the phenomenon.

Young Mr. and Mrs. Philip Vinson started housekeeping in what had once been a mansion. It was now a rundown eyesore.

It had belonged to Norah Vinson’s great-aunt Martha, who had left it to her in her will. The estate was in litigation, but the executor had permitted the Vinsons to settle down in the house, though they weren’t allowed yet to sell it. It had no modern conveniences, and was full of rooms they couldn’t use and heavy old-fashioned furniture; but it was solidly built and near the laboratory where he worked as a technician, and they could live rent-free until they could sell the house and use the money to buy a real home.

“Something funny happened in the lab last night,” Philip reported, watching Norah struggle with dinner on the massive coal-stove. “Somebody broke in and stole about half our experimental animals. And they got our pride and joy.”

“The famous SK540?” Norah asked.

“The same. Actually, it wasn’t a break-in. It must have been an inside job. The cages were open but there were no signs of breaking and entering. We’re all under suspicion till they find out who-dunit.”

Norah looked alarmed.

“You too? What on earth would anybody want with a lot of laboratory rats? They aren’t worth anything, are they--financially, I mean?”

“Not a cent. That’s why I’m sure one of the clean-up kids must have done it. Probably wanted them for pets. They’re all tame, of course, not like wild rats--though they can bite like wild rats if they want to. Some of the ones missing are treated, and some are controls. It would just be a nuisance if they hadn’t taken SK540. Now they’ve got to find him, or do about five years’ work over again, without any assurance of as great a success. To say nothing of letting our super-rat loose on the world.”

“What on earth could even a super-rat do that would matter--to human beings, I mean?”

“Nobody knows. Maybe that’s what we’re going to find out.”

That night Norah woke suddenly with a loud scream. Philip got the gas lighted--there was no electricity in the old house--and held her shaking body in his arms. She found her breath at last long enough to sob: “It was a rat! A rat ran right over my face!”

“You’re dreaming, darling. It’s because I told you about the theft at the lab. There couldn’t be rats in this place. It’s too solidly built, from the basement up.”

He finally got her to sleep again, but he lay awake for a long time, listening. Nothing happened.

Rats can’t talk, but they can communicate. About the time Norah Vinson dropped off after her frightened wakening, SK540 was confronting a culprit. The culprit was one of the liberated males. His beady eyes tried to gaze into the implacable ones of SK540, but his tail twitched nervously and if he bared his teeth it was more in terror than in fight. They all knew that strict orders had been given not to disturb the humans in the house until SK540 had all his preparations made.

A little more of that silent communication, and the rat who had run over Norah’s face knew he had only two choices--have his throat slit or get out. He got.

“What do you know?” Philip said that evening. “One of our rats came back.”

“By itself?”

“Yeah. I never heard of such a thing. It was one of the experimental ones, so it was smarter than most, though not such an awful lot. I never heard of a rat with homing instinct before. But when we opened up this morning, there he was, sitting in his cage, ready for breakfast.”

“Speaking of breakfast, I thought I asked you to buy a big box of oatmeal on your way home yesterday. It’s about the only thing in the way of cereal I can manage on that old stove.”

“I did buy it. Don’t you remember? I left it in the kitchen.”

“Well, it wasn’t there this morning. All I know is that you’re going to have nothing but toast and coffee tomorrow. We seem to be out of eggs, too. And bacon. And I thought we had half a pound left of that cheese, but that’s gone too.”

“Good Lord, Norah, if you’ve got that much marketing to do, can’t you do it yourself?”

“Sure, if you leave the car. I’m not going to walk all that way and back.”

So of course Philip did do the shopping the next day. Besides, Norah had just remembered she had a date at the hairdresser’s.

When he got home her hair was still uncurled and she was in hysterics. One of the many amenities great-aunt Martha’s house lacked was a telephone; anyway, Norah couldn’t have been coherent over one. She cast herself, shuddering and crying, into Philip’s arms, and it was a long time before he got her soothed enough for her to gasp: “Philip! They wouldn’t let me out!”

“They? Who? What do you mean?”

“The--the rats! The white rats. They made a ring around me at the front door so I couldn’t open it. I ran to the back and they beat me there and did the same thing. I even tried the windows but it was no use. And their teeth--they all--I guess I went to pieces. I started throwing things at them and they just dodged. I yelled for help but there’s nobody near enough to hear. Then I gave up and ran in our bedroom and slammed the door on them, but they left guards outside. I heard them squeaking till you drove up, then I heard them run away.”

Philip stared at her, scared to death. His wife had lost her mind.

“Now, now, sweetheart,” he said soothingly, “let’s get this straight. They fired a lab boy today. They found four of our rats in his home. He told some idiotic story of having ‘found’ them, with the others missing, running loose on the street that night, but of course he stole them. He must have sold the rest of them to other kids; they’re working on that now.”

Norah blew her nose and wiped her eyes. She had regained her usual calm.

“Philip Vinson,” she said coldly, “are you accusing me of lying, or just of being crazy? I’m neither. I saw and heard those rats. They’re here now. What’s more, I guess I know where that oatmeal went, and the eggs and bacon too, and the cheese. I’m--I’m a hostage!

“I don’t suppose,” she added sarcastically, “that your SK540 was one of the ones they found in the boy’s home?”

“No, it wasn’t,” he acknowledged uneasily. A nasty little icy trickle stole down his spine. “All right, Norah, I give in. You take the poker and I’ll take the hammer, and we’ll search this house from cellar to attic.”

“You won’t find them,” said Norah bitterly. “SK540’s too smart. They’ll stay inside the walls and keep quiet.”

“Then we’ll find the holes they went through and rout them out.”

They didn’t, of course. There wasn’t a sign of a rathole, or of a rat.

They got through dinner and the evening somehow. Norah put all the food not in cans inside the old-fashioned icebox which took the place of a refrigerator. Philip thought he was too disturbed to be able to sleep, but he did, and Norah, exhausted, was asleep as soon as her head touched the pillow.