The weatherman had promised a scorcher, and the heat that already lay like a blanket over the room made it seem probable the promise would be fulfilled. She moved listlessly, showering patting herself dry, lingering over the choice of a dress until her mother called urgently from the kitchen. She was long minutes behind schedule when she left the house. Usually she rather enjoyed easing her small car into the stream of automobiles pouring down Sepulveda toward the San Diego Freeway, jockeying for position, shifting expertly from one lane to another to take advantage of every break in the traffic. This morning she felt only angry impatience; she choked back on the irritated impulse to drive directly into the side of a car that cut across in front of her, held her horn button down furiously when a slow-starting truck hesitated fractionally after the light turned green. When she finally edged her Renault up on the "on" ramp and the freeway stretched straight and unobstructed ahead, she stepped down on the accelerator and watched the needle climb up and past the legal 65-mile limit. The sound of her tires on the smooth concrete was soothing and the rush of wind outside gave the morning an illusion of coolness. She edged away from the tangle of cars that had pulled onto the freeway with her and momentarily was alone on the road, with her rear-view mirror blank, the oncoming lanes bare, and a small rise shutting off the world ahead. That was when it happened. "Get out of the way!" a voice shrieked "out of the way, out of the way, OUT OF THE WAY!" Her heart lurched, her stomach twisted convulsively, and there was a brassy taste in her mouth. Instinctively, she stamped down on the brake pedal, swerved sharply into the outer lane. By the time she had topped the rise, she was going a cautious 50 miles an hour and hugging the far edge of the freeway. Then, and only then, she heard the squeal of agonized tires and saw the cumbersome semitrailer coming from the opposite direction rock dangerously, jackknife into the dividing posts that separated north and south-bound traffic, crunch ponderously through them, and crash to a stop, several hundred feet ahead of her and squarely athwart the lane down which she had been speeding only seconds earlier.