“What’s the matter?”

“I want to be sure she can’t hear us.”

“She? Nanny?”

Mary came toward him. “Tom, I woke up last night again. Because of the sounds. I heard them again, the same sounds, the sounds I heard before. And you told me it didn’t mean anything!”

Tom gestured. “It doesn’t. What does it mean?”

“I don’t know. That’s what worries me. But after we’re all asleep she comes downstairs. She leaves their room. She slips down the stairs as quietly as she can, as soon as she’s sure we’re all asleep.”

“But why?”

“I don’t know! Last night I heard her going down, slithering down the stairs, as quiet as a mouse. I heard her moving around down here. And then—”

“Then what?”

“Tom, then I heard her go out the back door. Out, outside the house. She went into the back yard. That was all I heard for awhile.”

Tom rubbed his jaw. “Go on.”

“I listened. I sat up in bed. You were asleep, of course. Sound asleep. No use trying to wake you. I got up and went to the window. I lifted the shade and looked out. She was out there, out in the back yard.”

“What was she doing?”

“I don’t know.” Mary Fields’s face was lined with worry. “I don’t know! What in the world would a Nanny be doing outside at night, in the back yard?”

It was dark. Terribly dark. But the infrared filter clicked into place, and the darkness vanished. The metal shape moved forward, easing through the kitchen, its treads half-retracted for greatest quiet. It came to the back door and halted, listening.

There was no sound. The house was still. They were all asleep upstairs. Sound asleep.

The Nanny pushed, and the back door opened. It moved out onto the porch, letting the door close gently behind it. The night air was thin and cold. And full of smells, all the strange, tingling smells of the night, when spring has begun to change into summer, when the ground is still moist and the hot July sun has not had a chance to kill all the little growing things.

The Nanny went down the steps, onto the cement path. Then it moved cautiously onto the lawn, the wet blades of grass slapping its sides. After a time it stopped, rising up on its back treads. Its front part jutted up into the air. Its eye stalks stretched, rigid and taut, waving very slightly. Then it settled back down and continued its motion forward.

It was just going around the peach tree, coming back toward the house, when the noise came.

It stopped instantly, alert. Its side doors fell away and its grapples ran out their full lengths, lithe and wary. On the other side of the board fence, beyond the row of shasta daisies, something had stirred. The Nanny peered, clicking filters rapidly. Only a few faint stars winked in the sky overhead. But it saw, and that was enough.

On the other side of the fence a second Nanny was moving, making its way softly through the flowers, coming toward the fence. It was trying to make as little noise as possible. Both Nannies stopped, suddenly unmoving, regarding each other—the green Nanny waiting in its own yard, the blue prowler that had been coming toward the fence.

The blue prowler was a larger Nanny, built to manage two young boys. Its sides were dented and warped from use, but its grapples were still strong and powerful. In addition to the usual reinforced plates across its nose there was a gouge of tough steel, a jutting jaw that was already sliding into position, ready and able.

Mecho-Products, its manufacturer, had lavished attention on this jaw-construction. It was their trademark, their unique feature. Their ads, their brochures, stressed the massive frontal scoop mounted on all their models. And there was an optional assist: a cutting edge, power-driven, that at extra cost could easily be installed in their “Luxury-line” models.

This blue Nanny was so equipped.

Moving cautiously ahead, the blue Nanny reached the fence. It stopped and carefully inspected the boards. They were thin and rotted, put up a long time ago. It pushed its hard head against the wood. The fence gave, splintering and ripping. At once the green Nanny rose on its back treads, its grapples leaping out. A fierce joy filled it, a bursting excitement. The wild frenzy of battle.

The two closed, rolling silently on the ground, their grapples locked. Neither made any noise, the blue Mecho-Products Nanny nor the smaller, lighter, pale-green Service Industries, Inc., Nanny. On and on they fought, hugged tightly together, the great jaw trying to push underneath, into the soft treads. And the green Nanny trying to hook its metal point into the eyes that gleamed fitfully against its side. The green Nanny had the disadvantage of being a medium-priced model; it was outclassed and outweighed. But it fought grimly, furiously.

On and on they struggled, rolling in the wet soil. Without sound of any kind. Performing the wrathful, ultimate task for which each had been designed.

“I can’t imagine,” Mary Fields murmured, shaking her head. “I just don’t know.”

“Do you suppose some animal did it?” Tom conjectured. “Are there any big dogs in the neighborhood?”

“No. There was a big red Irish setter, but they moved away, to the country. That was Mr. Petty’s dog.”

The two of them watched, troubled and disturbed. Nanny lay at rest by the bathroom door, watching Bobby to make sure he brushed his teeth. The green hull was twisted and bent. One eye had been shattered, the glass knocked out, splintered. One grapple no longer retracted completely; it hung forlornly out of its little door, dragging uselessly.

“I just don’t understand,” Mary repeated. “I’ll call the repair place and see what they say. Tom, it must have happened sometime during the night. While we were asleep. The noises I heard—”

“Shhh,” Tom muttered warningly. Nanny was coming toward them, away from the bathroom. Clicking and whirring raggedly, she passed them, a limping green tub of metal that emitted an unrhythmic, grating sound. Tom and Mary Fields unhappily watched her as she lumbered slowly into the living room. “I wonder,” Mary murmured.

“Wonder what?”

“I wonder if this will happen again.” She glanced up suddenly at her husband, eyes full of worry. “You know how the children love her … and they need her so. They just wouldn’t be safe without her. Would they?”

“Maybe it won’t happen again,” Tom said soothingly. “Maybe it was an accident.” But he didn’t believe it; he knew better. What had happened was no accident.

From the garage he backed his surface cruiser, maneuvered it until its loading entrance was locked against the rear door of the house. It took only a moment to load the sagging, dented Nanny inside; within ten minutes he was on his way across town to the repair and maintenance department of Service Industries, Inc.

The serviceman, in grease-stained white overalls, met him at the entrance. “Troubles?” he asked wearily; behind him, in the depths of the block-long building, stood rows of battered Nannies, in various stages of disassembly. “What seems to be the matter this time?”

Tom said nothing. He ordered the Nanny out of the cruiser and waited while the serviceman examined it for himself.

Shaking his head, the serviceman crawled to his feet and wiped grease from his hands. “That’s going to run into money,” he said. “The whole neural transmission’s out.”

His throat dry, Tom demanded: “Ever seen anything like this before? It didn’t break; you know that. It was demolished.”

“Sure,” the serviceman agreed tonelessly. “It pretty much got taken down a peg. On the basis of those missing chunks—” He indicated the dented anterior hull-sections. “I’d guess it was one of Mecho’s new jaw-models.”

Tom Fields’s blood stopped moving in his veins. “Then this isn’t new to you,” he said softly, his chest constricting. “This goes on all the time.”

“Well, Mecho just put out that jaw-model. It’s not half bad … costs about twice what this model ran. Of course,” the serviceman added thoughtfully, “we have an equivalent. We can match their best, and for less money.”