THE TALL MAN WHO WORE yellow-tinted glasses and cowboy boots and a weathered, smoke-colored Stetson made a mistake. While the clerk in a Lafayette pawnshop and gun store bagged up two boxes of.22 magnum shells for him, the man in the Stetson happened to notice a bolt-action military rifle up on the rack.

"That's an Italian 6.5 Carcano, ain't it? Hand it down here and I'll show you something," he said.

He wrapped the leather sling over his left arm, opened the bolt, and inserted his thumb in the chamber to make sure the gun was not loaded.

"This is the same kind Oswald used. Now, here's the mathematics. The shooter up in that book building had to get off three shots in five and a half seconds. You got a stopwatch?" he said.

"No," the clerk said.

"Here, look at my wristwatch. Now, I'm gonna dry-fire it three times. Remember, I ain't even aiming and Oswald was up six stories, shooting at a moving target."

"That's not good for the firing pin," the clerk said.

"It ain't gonna hurt it. It's a piece of shit anyway, ain't it?"

"I wish you wouldn't do that, sir."

The man in the Stetson set the rifle back on the glass counter and pinched his thumb and two ringers inside his Red Man pouch and put the tobacco in his jaw. The clerk's eyes broke when he tried to return the man's stare.

"You ought to develop a historical curiosity. Then maybe you wouldn't have to work the rest of your life at some little pissant job," the man said, and picked up his sack and started for the front door.

The clerk, out of shame and embarrassment, said to the man's back, "How come you know so much about Dallas?"

"I was there, boy. That's a fact. The puff of smoke on the grassy knoll?" He winked at the clerk and went out.

The clerk stood at the window, his face tingling, feeling belittled, searching in his mind for words he could fling out the door but knowing he would not have the courage to do so. He watched the man in the Stetson drive down the street to an upholstery store in a red pickup truck with Texas plates. The clerk wrote down the tag number and called the sheriffs department.

ON FRIDAY MORNING FATHER James Mulcahy rose just before dawn, fixed two sandwiches and a thermos of coffee in the rectory kitchen, and drove to Henderson Swamp, outside of the little town of Breaux Bridge, where a parishioner had given him the use of a motorized houseboat.

He drove along the hard-packed dirt track atop the levee, above the long expanse of bays and channels and flooded cypress and willows that comprised the swamp. He parked at the bottom of the levee, walked across a board plank to the houseboat, released the mooring ropes, and floated out from the willows into the current before he started the engine.

The clouds in the eastern sky were pink and gray, and the wind lifted the moss on the dead cypress trunks. Inside the cabin, he steered the houseboat along the main channel, until he saw a cove back in the trees where the bream were popping the surface along the edge of the hyacinths. When he turned into the cove and cut the engine, he heard an outboard coming hard down the main channel, the throttle full out, the noise like a chain saw splitting the serenity of the morning. The driver of the outboard did not slow his boat to prevent his wake from washing into the cove and disturbing the water for another fisherman.

Father Mulcahy sat in a canvas chair on the deck and swung the bobber from his bamboo pole into the hyacinths. Behind him, he heard the outboard turning in a circle, heading toward him again. He propped his pole on the rail, put down the sandwich he had just unwrapped from its wax paper, and walked to the other side of the deck.

The man in the outboard killed his engine and floated in to the cove, the hyacinths clustering against the bow. He wore yellow-tinted glasses, and he reached down in the bottom of his boat and fitted on a smoke-colored Stetson that was sweat-stained across the base of the crown. When he smiled his dentures were stiff in his mouth, the flesh of his throat red like a cock's comb. He must have been sixty-five, but he was tall, his back straight, his eyes keen with purpose.

"I'm fixing to run out of gas. Can you spare me a half gallon?" he said.

"Maybe your high speed has something to do with it," Father Mulcahy said.

"I'll go along with that." Then he reached out for an iron cleat on the houseboat as though he had already been given permission to board. Behind the seat was a paper bag stapled across the top and a one-gallon tin gas can.

"I know you," Father Mulcahy said.

"Not from around here you don't. I'm just a visitor, not having no luck with the fish."

"I've heard your voice."

The man stood up in his boat and grabbed the handrail and lowered his face so the brim of his hat shielded it from view.

"I have no gas to give you. It's all in the tank," Father Mulcahy said.

"I got a siphon. Right here in this bag. A can, too."

The man in the outboard put one cowboy boot on the edge of the deck and stepped over the rail, drawing a long leg behind him. He stood in front of the priest, his head tilted slightly as though he were examining a quarry he had placed under a glass jar.

"Show me where your tank's at. Back around this side?" he said, indicating the lee side of the cabin, away from the view of anyone passing on the channel.

"Yes," the priest said. "But there's a lock on it. It's on the ignition key."

"Let's get it, then, Reverend," the man said.

"You know I'm a minister?" Father Mulcahy said.

The man did not reply. He had not shaved that morning, and there were gray whiskers among the red and blue veins in his cheeks. His smile was twisted, one eye squinted behind the lens of his glasses, as though he were arbitrarily defining the situation in his own mind.

"You came to the rectory… In the rain," the priest said.

"Could be. But I need you to hep me with this chore. That's our number one job here."

The man draped his arm across the priest's shoulders and walked him inside the cabin. He smelled of deodorant and chewing tobacco, and in spite of his age his arm was thick and meaty, the crook of it like a yoke on the back of the priest's neck.

"Your soul will be forfeit," the priest said, because he could think of no other words to use.

"Yeah, I heard that one before. Usually when a preacher was trying to get me to write a check. The funny thing is, the preacher never wanted Jesus's name on the check."

Then the man in the hat pulled apart the staples on the paper bag he had carried on board and took out a velvet curtain rope and a roll of tape and a plastic bag. He began tying a loop in the end of the rope, concentrating on his work as though it were an interesting, minor task in an ordinary day.

The priest turned away from him, toward the window and the sun breaking through the flooded cypress, his head lowered, his fingers pinched on his eyelids.

The parishioner's sixteen-gauge pump shotgun was propped just to the left of the console. Father Mulcahy picked it up and leveled the barrel at the chest of the man in the Stetson hat and clicked off the safety.

"Get off this boat," he said.

"You didn't pump a shell into it. There probably ain't nothing in the chamber," the man said.

"That could be true. Would you like to find out?"

"You're a feisty old rooster, ain't you?"

"You sicken me, sir."

The man in yellow-tinted glasses reached in his shirt pocket with his thumb and two fingers and filled his jaw with tobacco.

"Piss on you," he said, and opened the cabin door to go back outside.

"Leave the bag," the priest said.