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.