Lightning

so in the hope of saving Danny. However, they had learned that a time traveler could not revisit a place if he scheduled his second arrival shortly
before
his previous jaunt; there was a natural mechanism that prevented a traveler from being in a place where he might encounter himself on a previous jaunt. He could return to Big Bear
after
he had left Laura that January night, for having already departed from the highway, he was no longer at risk of encountering himself there. But if he set the gate for an arrival time that would make it possible for him to meet himself, he would simply bounce back to the institute without going anywhere. That was one of many mysterious aspects of time travel which they had learned, around which they worked, but which they did not understand.
    When he finished programming the gate, he glanced at the latitude and longitude indicator to confirm that he would arrive in the general area of Big Bear. Then he looked at the clock that noted his arrival time, and he was startled to see that it showed 8:00 p.m., January 10, 1989, instead of 1988. The gate was now set to deliver him to Big Bear not hours after Danny's death but a full year later.
    He was sure that his calculations were correct; he'd had plenty of time to make them and recheck them over the past couple of weeks. Evidently, nervous as he was, he had made a mistake when entering the numbers. He would have to reprogram the gate.
    Less than three minutes until detonation.
    He blinked sweat out of his eyes and studied the numbers on the paper, the end product of his extensive calculations. As he reached for a control knob to cancel out the current program and re-enter the first of the figures again, a shout of alarm went up in the ground-floor corridor. The cries sounded as if they were coming from the north end of the building, in the general area of the document room.
    Someone had found the bodies of Januskaya and Volkaw. He heard more shouting. People running. Glancing nervously at the closed door to the hall, he decided he had no time to reprogram. He would have to settle for returning to Laura one year after he had last left her.
    With the silencer-fitted Colt Commander in his right hand, he rose from the programming console and headed toward the gate—that eight-foot-high, twelve-foot-long, polished steel, open-ended barrel resting a foot off the floor on copper-plated blocks. He did not even want to risk taking time to recover his peacoat from the corner where he had left it an hour ago. The commotion in the corridor was louder. When he was only a couple of steps from the entrance to the gate, the lab door was thrown open behind him with such force that it hit the wall with a crash. "Stop right there!"
    Stefan recognized the voice, but he did not want to believe what he heard. He brought up the pistol as he swung around to confront his challenger: The man who had raced into the lab was Kokoschka.
    Impossible. Kokoschka was dead. Kokoschka had followed him to Big Bear on the night of January 10, 1988, and he had killed Kokoschka on that snowswept highway.
    Stunned, Stefan squeezed off two shots, both wide.
    Kokoschka returned his fire. One slug took Stefan in the chest, high on the left side, knocking him backward against the edge of the gate. He stayed on his feet and got off three shots at Kokoschka, forcing the bastard to dive for cover and roll behind a lab bench.
    There were less than two minutes from detonation.
    Stefan felt no pain because he was in shock. But his left arm was useless; it hung limply at his side. And an insistent, oily blackness seeped in at the edges of his vision.
    Only a few overhead lights had been left on, but suddenly even they flickered and went out, leaving the room vaguely illuminated by the wan glow of the many glass-covered dials and gauges.
    For an instant Stefan thought the dying light was a further surrender of his consciousness, a subjective development, but then he realized the public power supply had failed again, evidently due to the work of saboteurs, for there had been no sirens to warn of an air attack.
    Kokoschka fired twice from darkness, the muzzle flash marking his position, and Stefan loosed the last three rounds in his pistol, though there was no hope of hitting Kokoschka through the marble lab bench.
    Thankful that the gate was powered by a secure generator and still functional, Stefan threw away the pistol and with his good hand gripped the rim of the barrel-shaped portal.