Watchers

backdrops of rocks or plants, snug against the trunks of a few trees, at the corners of the house, and beside an old rotting pine stump at the edge of the driveway. He had bought the components on the open market, from an electronics dealer in San Francisco. It was dated stuff, not at all state-of-the-art security technology, but he chose it because he was familiar with it from his days in Delta Force, and it was good enough for his purposes. Lines from the sensors ran underground, to an alarm box in one of the kitchen cupboards. When the system was switched on at night, nothing larger than a raccoon could come within thirty feet of the house—or enter the barn at the back of the property—without tripping the alarm. No bells would ring, and no sirens would blare because that would alert The Outsider and might run it off. They didn’t want to chase it away; they wanted to kill it. Therefore, when the system was tripped, it turned on clock radios in every room of the house, all of which were set at low volume so as not to frighten off an intruder but high enough to warn Travis and Nora.
    Today, all the sensors were in place, as usual. All he had to do was wipe off the light film of dust that had coated the lenses.
    “The palace moat is in good repair, m’lord,” Travis said.
    Einstein woofed approval.
    In the rust-red barn, Travis and Einstein examined the equipment that, they hoped, would provide a nasty surprise for The Outsider.
    In the northwest corner of the shadowy interior, to the left of the big rolling door, a pressurized steel tank was clamped in a wall rack. In the diagonally opposite southeast corner at the back of the building, beyond the pickup and car, an identical vessel was bolted to an identical rack. They resembled large propane tanks of the sort people used at summer cabins for gas cooking, but they did not hold propane. They were filled with nitrous oxide, which was sometimes inaccurately called “laughing gas.” The first whiff did exhilarate you and make you want to laugh, but the second whiff knocked you out before the laugh could escape your lips. Dentists and surgeons frequently used nitrous oxide as an anesthetic. Travis had purchased it from a medical-supply house in San Francisco.
    After switching on the barn lights, Travis checked the gauges on both tanks. Full pressure.
    In addition to the large rolling door at the front of the barn, there was a smaller, man-size door at the rear. These were the only two entrances. Travis had boarded over a pair of windows in the loft. At night, when the alarm system was engaged, the smaller rear door was left unlocked in the hope that The Outsider, intending to scout the house from the cover of the barn, would let itself into the trap. When it opened the door and crept into the barn, it would trigger a mechanism that would slam and lock the door behind it. The front door, already locked from outside, would prevent an exit in that direction.
    Simultaneous with the springing of the trap, the large tanks of nitrous oxide Would release their entire contents in less than one minute because Travis
    had fitted them with high-pressure emergency-release valves tied in with the alarm system. He had caulked all of the draft-admitting cracks in the barn and had insulated the place as thoroughly as possible in order to insure that the nitrous oxide would be contained within the structure until one of the doors was unlocked from outside and opened to vent the gas.
    The Outsider could not take refuge in the pickup or the Toyota, for they would be locked. No corner in the barn would be free of the gas. Within less than a minute, the creature would collapse. Travis had considered using poisonous gas of some kind, which he probably could have obtained on the underground market, but he had decided against going to that extreme because, if something went wrong, the danger to him and Nora and Einstein would be too great.
    Once gas had been released and The Outsider had succumbed, Travis could simply open one of the doors, vent the barn, enter with the Uzi carbine, and kill the beast where it lay unconscious. At worst, even if the time taken airing out the building gave The Outsider a chance to regain consciousness, it would still be groggy and disoriented and easily dispatched.
    When they had ascertained that everything in the barn was as it should be, Travis and Einstein returned to the yard behind the house. The December day was cool but windless. The forest