The hedgehogs unarguably made looking out for themselves easier. "R2D2 on steroids" is how Thibodeau described them, and in its own way that was an apt representation. Their omnidirectional color video cameras were encased in rounded turrets atop vertical racks or "necks," giving them a vaguely anthropomorphic appearance that many female staffers found cute--as did quite a few of the plant's male employees, though rarely by open admission. Mounted on tracked 6x6 drive platforms, they were quick, quiet, and capable of maneuvering across everything from narrow corridors and stairwells to rugged, heavily obstacled outdoor terrain. Products of UpLink's own R&D, they boasted a wide range of proprietary hardware-and-software-based systems. Their hazard/intruder detection array included broad-spectrum gas, smoke, temperature, optical flame, microwave radar, vehicular sonar, passive infrared, seismic, and ambient light sensors. Their clawed, retractable gripper arms were strong enough to lift twenty-five-pound objects and precise enough to pick the smallest coins up off the ground.

Nor were the hedgehogs limited to merely sounding the alarm should they find something amiss. They were, rather, midnight riders and first-wave militia rolled into one, ready to neutralize threats ranging from chemical fires to trespassers on command. Packed aboard their chassis were fluid cannons that could unleash highpressure jets of water, polymer superglues, and anti-traction superlubricants; 12-gauge sidewinder shotguns loaded with disabling aerosol cartridges; laser-dazzler and visual stimulus and illusion banks; and other fruits of UpLink's ambitious nonlethal weapons program.

There were a total of six hedgehogs at the Brazilian compound, four posted near the borders of its approximately rectangular grounds, an additional pair safeguarding its central buildings. Each of the ground patrols encompassed an entire perimeter line and a parallel sector reaching inward for one hundred meters, and each mechanical sentry on that beat had been given a nickname whose first initial corresponded with the first letter of the direction it covered: Ned toured the northern perimeter, Sammy the compound's south side, Ed its eastern margin, Wally its western. The two indoor sentries were Felix and Oscar, assigned to the factory and office complexes respectively. On average, a hedgehog would patrol for eight to ten hours at a stretch before having to recharge its nickel-cadmium batteries at one of the docking stations along its route, with more frequent pauses in the event of an increased task load.

And so they went about their rounds, smooth-running and tireless, responding to an anomalous motion here, an unusual variation in temperature there, investigating whatever seemed not to belong, relaying a stream of environmental data to monitoring stations attended by their human supervisors, and alerting them to any sign of danger or unauthorized entry along the fenced-in margins of the compound.

An invasion from above, however, was another matter altogether.

The hedgehog was midway through its third tour of the facility's western quadrant when its infrared sensors picked up a wavelength reading of twelve to fourteen microns--the distinctive heat signature of a human being--some fifty yards in front of it.

The robot paused, tracking the emission source, but it had quickly backed out of sensor range.