A hundred yards offshore, the fish sensed a change in the sea’s rhythm. It did not see the woman, nor yet did it smell her. Running within the length of its body were a series of thin canals, filled with mucus and dotted with nerve endings, and these nerves detected vibrations and signaled the brain. The fish turned toward shore.

The woman continued to swim away from the beach, stopping now and then to check her position by the lights shining from the house. The tide was slack, so she had not moved up or down the beach. But she was tiring, so she rested for a moment, treading water, and then started for shore.

The vibrations were stronger now, and the fish recognized prey. The sweeps of its tail quickened, thrusting the giant body forward with a speed that agitated the tiny phosphorescent animals in the water and caused them to glow, casting a mantle of sparks over the fish.

The fish closed on the woman and hurtled past, a dozen feet to the side and six feet below the surface. The woman felt only a wave of pressure that seemed to lift her up in the water and ease her down again. She stopped swimming and held her breath. Feeling nothing further, she resumed her lurching stroke.

The fish smelled her now, and the vibrations—erratic and sharp—signaled distress. The fish began to circle close to the surface. Its dorsal fin broke water, and its tail, thrashing back and forth, cut the glassy surface with a hiss. A series of tremors shook its body.

For the first time, the woman felt fear, though she did not know why. Adrenaline shot through her trunk and her limbs, generating a tingling heat and urging her to swim faster. She guessed that she was fifty yards from shore. She could see the line of white foam where the waves broke on the beach. She saw the lights in the house, and for a comforting moment she thought she saw someone pass by one of the windows.

The fish was about forty feet from the woman, off to the side, when it turned suddenly to the left, dropped entirely below the surface, and, with two quick thrusts of its tail, was upon her.

At first, the woman thought she had snagged her leg on a rock or a piece of floating wood. There was no initial pain, only one violent tug on her right leg. She reached down to touch her foot, treading water with her left leg to keep her head up, feeling in the blackness with her left hand. She could not find her foot. She reached higher on her leg, and then she was overcome by a rush of nausea and dizziness. Her groping fingers had found a nub of bone and tattered flesh. She knew that the warm, pulsing flow over her fingers in the chill water was her own blood.

Pain and panic struck together. The woman threw her head back and screamed a guttural cry of terror.