AT EIGHT in the morning of his last day in Boston, Sean Burke paced out tight circles on the corner of Kenmore Square, waiting for the abortionist, a nine-millimeter semiautomatic handgun hidden in the inside pocket of his army jacket.

Sean knew his enemy from the demonstrations-- a slight man with brown wisps of hair and hollow cheekbones, gray soulless eyes that ignored the pickets even when they cried out, "Don't kill me, Mommy and Daddy," in the imagined voice of a fetus. Part of Sean prayed for him to come; that other part, frightened and irresolute, hoped he would not. He encouraged himself by imagining the faces of the children he would save.

He passed forty minutes this way. With each moment, Sean felt more anxious.

And then the man was there, emerging from the subway.

The abortionist's hands were in his coat pockets. His eyes focused on the sidewalk, and his breaths became thin puffs in the surprising chill of a bright April day. He did not notice Sean.

Sean swallowed. His throat was dry, his mouth sour, the pit of his stomach clenched and raw. Clumsily, he reached a gloved hand into his left pocket and popped the last antacid pill into his mouth, teeth grinding it to chalk.

Dr. Bowe disappeared inside the building.

It was an old brownstone hotel, converted to offices for doctors, dentists, milliners, discount jewelers; passing through the double glass doors, a pregnant woman could be shopping for a necklace, not seeking an accomplice to help murder her unborn child. Sean knew only that the offices were on the first floor: because of a court order, pickets were required to stay outside and keep the walkway clear. The red carpet, their leader, Paul Terris, had named it. But neither Paul's exhortations nor all their protests had stopped the flow of blood.

Yet Sean stood there, still afraid. The chalk in his mouth tasted bitter.

If Sean acted, he would have to leave all he knew behind: the comfort of the church where he served as caretaker; the room above the parish offices, his home for three years now; the compassion of Father Brian Shaw, who praised his work and worried, in his soft-voiced way, about Sean's "intensity." In the newspapers and on television, in the streets and the bars of Charlestown, they would call Sean a murderer.

Let God be his judge, then. God and the children.

But Sean stood frozen, a slender man, with lank black hair and pale-blue eyes. Alone, as he had felt almost all his life, Sean watched the random pageant of the city pass him by: tardy workers rushing from the subway; cars honking; students heading for Boston University; an Asian nanny with a plaid wool scarf at her throat, pushing a baby in a blue carriage. They did not notice him and would not have understood had they known.

Then he saw her-- a young woman in a wool coat, knit cap pulled tight over her curly red hair, her face more Irish than Sean's own. He could imagine her sitting next to him in school.

Pausing on the sidewalk, she gazed at the double glass doors beneath the letters that spelled "Kenmore Building." Sean could feel her reluctance as intensely as he felt his own.

She was there for the abortionist, Sean was certain. Her back to Sean, she seemed barely to move. In his mind they were coupled: if she did not enter, perhaps Sean would grant the clinic a reprieve. Just for today.

Please, he murmured, save your baby. He prayed she was not one of them.

With a shrug, so small that Sean perhaps imagined it, the young woman walked toward the door.

Sean felt the anger come. If she was not worthy of the life she bore, then he must be.

Oblivious to traffic, Sean crossed the street. As he touched it, the gun in his pocket reassured him.

On the Saturday before last, he had driven to New Hampshire and bought the weapon at a package store: the same model, the owner informed him, that the Turkish guy had used to shoot the Pope-- small, light, easy to conceal. Sean stifled his dislike. "God bless the Holy Father," he said simply.

In the woods nearby, Sean had practiced.

Aiming the gun, he had imagined looking into his victim's face, blocking out all doubt, all fears. His aim had been good-- first trees, then rocks, then a careless squirrel which had almost vanished in a single shot. But now Sean's hand shook.

He was five feet from the door, then four feet. Each step felt leaden.

He must remember the lessons of history, Sean told himself. If he could have murdered Hitler, the Nazis would have called him a criminal, reviled the name Sean Burke. Perhaps Göring and the others would have hung him on a meat hook. And, perhaps, millions of others would have lived-- Jews and Slavs, Gypsies and children ...

Damp with sweat, Sean paused in front of the door, taking a last deep breath of morning air.

He walked into the dim hallway, looking to both sides. He saw a travel agency, an accountant's office. And then he found it.

A green laminate door with metal letters: "The Boston Women's Clinic." Since the demonstrations had failed, the abortionists in their arrogance no longer had a guard there.

Sean took the wool cap from his inside pocket and pulled it over his head.

For a last moment, his left hand rested on the doorknob. He made himself imagine the red-haired girl, nervously waiting for the abortionist to put a plastic tube between her legs and suck the life from her womb.

Sean murmured a final prayer and opened the door.

The girl was there. She gazed up at him from behind her magazine, as if surprised. With her cap off, her hair was a riot of red curls.

"Yes?" the receptionist asked.

Sean turned to her-- a vulpine older woman with hair dyed a frightening black and lipstick as red as blood.

Softly, he said, "I'm here for Dr. Bowe."

The skin of her face was pale as parchment. She stared up at him from her swivel chair, still but for her left hand. There was a panic button beneath her desk, someone had told him; the day the others had occupied the waiting room, she had used it to call security.

"Don't." Sean's voice was harsh now. The red-haired girl dropped her magazine.

The receptionist's throat moved in a convulsive swallow, choking her words. "What do you want?"

Sean took out his gun. "To stop you," he answered, and pulled the trigger.

It was a kind of magic. As her head snapped back, a hole opened in her forehead. There was a soft concussive sound, like a melon hitting cement, almost lost in the red-haired girl's cry.

Sean stared in stupefaction as the woman died in front of him, blood trickling from her forehead. Only when she hit the carpet did Sean turn to the girl.

"Don't move." His voice came out panicky, too high. Gun in hand, he stumbled down the hallway.

The abortionist was in the room where he did his work, bent over a metal cabinet in the corner. Sean stared at him, then at the table covered in white paper, the altar where women sacrificed the innocent. His hand trembled as he raised the gun.

Dr. Bowe barely had time to peer sideways before Sean shot at his temple.

The red stain appeared. Sean watched in near astonishment as the abortionist fell to his knees, face pitching forward into the files of his victims. Only then did Sean register the melon sound again.

With a rush of anger, Sean lifted Bowe's warm twitching body and threw him onto the table, wrenching his legs open in the spraddle of all the women whose children he had murdered. The abortionist's eyes were glazed, his mouth agape, as if protesting this indignity.

Sean heard a gasp behind him.

A nurse stood in the door, a stethoscope around her neck, mouth forming words that would not come. Sean did not want to kill her; she was a tool, like the receptionist. But he had no choice.

"I'm sorry," he murmured, and shot her in the chest. The nurse crumpled in the doorway, then was still.

Sean stepped across her body, looking down at her. At least her family, if she had one, could gaze into her face without flinching. Sean walked down the hallway in a trance.

The red-haired young woman shivered on the couch, staring at the dead receptionist, too frightened to move. Tears streamed down her face. Sean could not bring himself to kill the life inside her.

Sean knelt in front of her, giving comfort, seeking it. "I had to stop him. Your sympathy should be with your baby, the life I came to save."

Comprehension filled her eyes. "I'm not pregnant," she stammered.

Sean felt the blood rush to his face. He stood, humiliated and confused, blood pounding like a trip-hammer in his temples. His finger squeezed the trigger.

"Please. I only came here for an IUD ..."

Sean dropped his gun and ran from the building.

THERE WAS a subway station at the corner.

Sean rushed down the stairs and through the turnstile. Some vestige of discipline made him find the men's room, leave his jacket, gloves, and wool cap in a stall, and walk to the platform with a numb unhurried stride, a young man in a Holy Cross sweatshirt.

Take the green line to Court Street, then transfer to blue. He recited this like a rosary as the subway stopped and he boarded the half-empty car. No one looked at him.

She was lying. Sean had saved her baby, and she had lied to save herself, believing he would think it less damning to thwart life with a piece of plastic. Perhaps Sean had taught her better.

Dazed, he imagined the sirens screaming as the cars arrived at Kenmore Square. At Court Street, the subway doors hissed open. Arms folded, head bowed, Sean walked out and waited in the dingy tunnel, a portrait of urban anonymity.

He had asked Father Brian if he could take a week's vacation in New Hampshire. "Surely," the priest had answered in his mild way, "but is early April a good time? The mud season, they call it in New England."

Within minutes, the subway for Logan Airport came.

SEAN'S SUITCASE was in a locker at the airport.

He pulled it out. If his plan worked, the last trace of him found in Boston would be the jacket, the hat, the gloves. Remorse mingled with relief now at the lifting of his burden: he no longer stood watch, armed only with signs and slogans, while children died.

Face pinched, he went through security at Gateway C.

No one stopped him. He headed for the gate with his scuffed black suitcase, surrounded by vacationers, students on spring break, commercial travelers leaving their homes. But the only person in line was a black woman with glasses and a briefcase. Uncomfortable, Sean hung back until she was finished.

The blond ticket agent raised her eyebrows. "Next?"

There was a hint of challenge, Sean thought. This might be the end: the red-haired woman could describe him, and he was certain that the police kept files on Operation Life.

"Next?" she repeated, impatient now, studying his face.

Sean pulled the ticket from his back pocket and placed it on the counter.

She flipped it open. "Mr. Burke," she said. "Photo ID, please."

Sean took out his wallet. To his own eyes, the photo on his driver's license looked furtive. For a long moment, the ticket agent looked from Sean to his photo and back again.

One call, he thought. The airport swarmed with cops and blue-uniformed security officers. His palms felt moist.

"Did you pack your luggage yourself?" she asked.

"Yes."

"One bag?"

"Yes."

"Did someone you did not know give you anything to carry?"

Sean drew a breath. "I wouldn't do that," he said.

The ticket agent hesitated, watching him. "Zone C," she told him. "Seat twenty-five B. They board about one-fifteen."

Once on the plane, Sean realized, he would be trapped. He did not board until the final call.

AT TWO o'clock, the plane had not taken off.

A mechanical problem, the pilot explained in his John Wayne voice-- a systems light that won't come on, probably just an electrical short. Sit tight and I'll keep you posted.

Sean bowed his head. They were holding him, Sean thought. At any moment, they would evacuate the plane and clap handcuffs on his wrists. The feeling came to him again: he was a small and lonely boy, terrified of his father, despairing for his mother's blank indifference. There was no safe place for him.

Sean stood abruptly. He reeled to the rear bathroom, past the other passengers, their faces weary, trapped, indifferent.

His own face in the mirror was white. When the retching started, racking his body, all he saw in the basin was saliva and traces of blood. The bathroom felt like a closet.

Sean opened the door, gulping for breath.

Slowly, he returned to his seat. He kept his eyes averted from the woman sitting next to him.

Ten minutes later, the pilot made his final announcement. Then the plane lifted into the air, vibrating with power, and Sean Burke left Boston forever.