Strangers

snow, he took a deep breath and found that the Latin phrases came to his tongue without hesitation.
        

        
        The crawl-through that Jack had cut in the chainlink fence was small, but none of them - Jack, Dom, or Ginger - was a large person, so they all squeezed onto the grounds of Thunder Hill without difficulty, having pushed the rucksacks full of equipment ahead of them.
        At Jack's direction, Dom and Ginger stayed close to the fence until he had a chance to study the immediate landscape through the Star Tron night-vision device. He was searching for posts on which surveillance cameras and photoelectric-cell alarm systems might be rigged. Though blowing snow made the inspection more difficult than it would have been in better weather, he located two poles on which were mounted cameras that covered this portion of the Thunder Hill perimeter from different angles. He believed the lenses of both cameras were filmed with snow, though due to the storm he could not be certain. He saw no evidence of photoelectric systems to detect movement across this part of the meadow.
        Next, from a zippered pocket, he withdrew a wallet-size device - an extremely sophisticated variation of a voltameter. It could detect the passage of electric current through a line without making contact with that line, although it could not measure the strength of the current.
        He turned toward the open meadow, putting his back to the fence. Crouching, he held the object out at arm's length, about two feet above the ground, and moved slowly forward. The voltage detector would register a current from lines buried as deep as eighteen inches underground, unless they were sheathed in pipes. The kind of lines he was looking for were neither that deep nor sheathed. Even the foot of new and old snow would not measurably affect the device's performance. He edged forward only about three yards before the detector began beeping softly and flashing its amber light.
        He halted immediately, stepped back a couple of feet, and called Dom and Ginger to his side. They huddled together, and Jack said, "There's a pressure-sensitive alarm grid buried an inch or two under the ground. It starts about ten feet inside the fence, and I'm sure it runs parallel to the fence all around the facility. It's a web of wires - sealed in thin plastic - that carry a low-voltage current. It's designed so the connections of some of the wires will be broken and the current interrupted if anything above a certain weight - oh, say fifty pounds - steps on them. The weight of the snow doesn't affect it because that's evenly distributed. It reacts to localized pressure - like a footstep."
        "Even I weigh more than fifty pounds," Ginger said. "How wide's this alarm grid?"
        "At least eight or ten feet," Jack said. "They want to be sure that if someone immensely clever like me should come along and detect the system, it'll be impossible just to jump across it."
        "I don't know about you," Dom said, "but I can't fly across."
        "I'm not so sure you can't," Jack said. "I mean, if you had time to explore that power Of yours… If you can levitate chairs, why couldn't you levitate yourself?" He saw this suggestion had startled Dom. "But you haven't time to learn to control your power, so we'll have to rely on what's gotten us this far."
        "What's that?" Ginger asked.
        "My genius," Jack said with a grin. "Here's what we'll do. We'll walk along the perimeter, staying in the safe ground between the fence and the alarm grid, until we find a place where there's a big sturdy tree standing twenty or thirty feet deeper in the meadow, well beyond the width of the grid."
        "Then?" Dom asked.
        "You'll see."
        "What if we don't find a tree?" Ginger asked.
        "Doc," Jack said, "I had you pegged as a go-getting optimist. If I say we need a tree, I'd expect you to tell me we'll find a forest and have a thousand to choose from."
        They found the tree only three hundred yards down the slope toward the valley floor. It was a huge pine of such age and character that it offered the thick and widely separated limbs that Jack required. It towered eighty feet or higher, a snow-dusted monolith looming out of the storm, and it was thirty or thirty-five feet back from the fence, well beyond the farther edge of the alarm grid.
        Using the Star Tron again, Jack studied the massive pine until he