“When I look back,” Mary Fields said, “I marvel that we ever could have grown up without a Nanny to take care of us.”

There was no doubt that Nanny had changed the whole life of the Fields’s house since she had come. From the time the children opened their eyes in the morning to their last sleepy nod at night, Nanny was in there with them, watching them, hovering about them, seeing that all their wants were taken care of.

Mr. Fields knew, when he went to the office, that his kids were safe, perfectly safe. And Mary was relieved of a countless procession of chores and worries. She did not have to wake the children up, dress them, see that they were washed, ate their meals, or anything else. She did not even have to take them to school. And after school, if they did not come right home, she did not have to pace back and forth in anxiety, worried that something had happened to them.

Not that Nanny spoiled them, of course. When they demanded something absurd or harmful (a whole storeful of candy, or a policeman’s motorcycle) Nanny’s will was like iron. Like a good shepherd she knew when to refuse the flock its wishes.

Both children loved her. Once, when Nanny had to be sent to the repair shop, they cried and cried without stopping. Neither their mother nor their father could console them. But at last Nanny was back again, and everything was all right. And just in time! Mrs. Fields was exhausted.

“Lord,” she said, throwing herself down. “What would we do without her?”

Mr. Fields looked up. “Without who?”

“Without Nanny.”

“Heaven only knows,” Mr. Fields said. After Nanny had aroused the children from sleep—by emitting a soft, musical whirr a few feet from their heads—she made certain that they were dressed and down at the breakfast table promptly, with faces clean and dispositions unclouded. If they were cross Nanny allowed them the pleasure of riding downstairs on her back.

Coveted pleasure! Almost like a roller coaster, with Bobby and Jean hanging on for dear life and Nanny flowing down step by step in the funny rolling way she had.

Nanny did not prepare breakfast, of course. That was all done by the kitchen. But she remained to see that the children ate properly and then, when breakfast was over, she supervised their preparations for school. And after they had got their books together and were all brushed and neat, her most important job: seeing that they were safe on the busy streets.

There were many hazards in the city, quite enough to keep Nanny watchful. The swift rocket cruisers that swept along, carrying businessmen to work. The time a bully had tried to hurt Bobby. One quick push from Nanny’s starboard grapple and away he went, howling for all he was worth. And the time a drunk started talking to Jean, with heaven knows what in mind. Nanny tipped him into the gutter with one nudge of her powerful metal side.

Sometimes the children would linger in front of a store. Nanny would have to prod them gently, urging them on. Or if (as sometimes happened) the children were late to school, Nanny would put them on her back and fairly speed along the sidewalk, her treads buzzing and flapping at a great rate.

After school Nanny was with them constantly, supervising their play, watching over them, protecting them, and at last, when it began to get dark and late, dragging them away from their games and turned in the direction of home.

Sure enough, just as dinner was being set on the table, there was Nanny, herding Bobby and Jean in through the front door, clicking and whirring admonishingly at them. Just in time for dinner! A quick run to the bathroom to wash their faces and hands.

And at night—

Mrs. Fields was silent, frowning just a little. At night … “Tom?” she said.

Her husband looked up from his paper. “What?”

“I’ve been meaning to talk to you about something. It’s very odd, something I don’t understand. Of course, I don’t know anything about mechanical things. But Tom, at night when we’re all asleep and the house is quiet, Nanny—”

There was a sound.

“Mommy!” Jean and Bobby came scampering into the living room, their faces flushed with pleasure. “Mommy, we raced Nanny all the way home, and we won!”

“We won,” Bobby said. “We beat her.”

“We ran a lot faster than she did,” Jean said.

“Where is Nanny, children?” Mrs. Fields asked.

“She’s coming. Hello, Daddy.”

“Hello, kids,” Tom Fields said. He cocked his head to one side, listening. From the front porch came an odd scraping sound, an unusual whirr and scrape. He smiled.

“That’s Nanny,” Bobby said.

And into the room came Nanny.

Mr. Fields watched her. She had always intrigued him. The only sound in the room was her metal treads, scraping against the hardwood floor, a peculiar rhythmic sound. Nanny came to a halt in front of him, stopping a few feet away. Two unwinking photocell eyes appraised him, eyes on flexible wire stalks. The stalks moved speculatively, weaving slightly. Then they withdrew.

Nanny was built in the shape of a sphere, a large metal sphere, flattened on the bottom. Her surface had been sprayed with a dull green enamel, which had become chipped and gouged through wear. There was not much visible in addition to the eye stalks. The treads could not be seen. On each side of the hull was the outline of a door. From these the magnetic grapples came, when they were needed. The front of the hull came to a point, and there the metal was reinforced. The extra plates welded both fore and aft made her look almost like a weapon of war. A tank of some land. Or a ship, a rounded metal ship that had come up on land. Or like an insect. A sowbug, as they are called.

“Come on!” Bobby shouted.

Abruptly Nanny moved, spinning slightly as her treads gripped the floor and turned her around. One of her side doors opened. A long metal rod shot out. Playfully, Nanny caught Bobby’s arm with her grapple and drew him to her. She perched him on her back. Bobby’s legs straddled the metal hull. He kicked with his heels excitedly, jumping up and down.

“Race you around the block!” Jean shouted. “Giddup!” Bobby cried. Nanny moved away, out of the room with him. A great round bug of whirring metal and relays, clicking photocells and tubes. Jean ran beside her. There was silence. The parents were alone again. “Isn’t she amazing?” Mrs. Fields said. “Of course, robots are a common sight these days. Certainly more so than a few years ago. You see them everywhere you go, behind counters in stores, driving buses, digging ditches—”

“But Nanny is different,” Tom Fields murmured.

“She’s—she’s not like a machine. She’s like a person. A living person. But after all, she’s much more complex than any other kind. She has to be. They say she’s even more intricate than the kitchen.”

“We certainly paid enough for her,” Tom said.

“Yes,” Mary Fields murmured. “She’s very much like a living creature.” There was a strange note in her voice. “Very much so.”

“She sure takes care of the kids,” Tom said, returning to his newspaper.

“But I’m worried.” Mary put her coffee cup down, frowning. They were eating dinner. It was late. The two children had been sent up to bed. Mary touched her mouth with her napkin. “Tom, I’m worried. I wish you’d listen to me.”

Tom Fields blinked. “Worried? What about?”

“About her. About Nanny.”

“Why?”

“I—I don’t know.”

“You mean we’re going to have to repair her again? We just got through fixing her. What is it this time? If those kids didn’t get her to—”

“It’s not that.” “What, then?”

For a long time his wife did not answer. Abruptly she got up from the table and walked across the room to the stairs. She peered up, staring into the darkness. Tom watched her, puzzled.