Two-Legged Swamp Rats : A dreamy outpost where strangeness joins love : THE SHARPSHOOTER BLUES, <i> By Lewis Nordan (Algonquin Books of Chapel Hill: $17.95; 300 pp.)</i>

I was on the beach finishing “The Sharpshooter Blues” when some people came up and asked what I was reading. I told them it was the story of a hydrocephalic, brain-damaged kid called Hydro, who lives with his father in a fish-camp in a very strange swamp outside Arrow Catcher, Miss.

In this swamp there are monkeys and parrots in the trees, and porpoises in the mineral-rich water. Hydro’s father has given the porpoises pet names like Sister Woman and Renford and Lamar and St. Elmo. I think it was the porpoise detail that did it; the people kind of smiled and said “well!” and “enjoy!” and generally moved on down the beach, which was what I wanted them to do, so I could re-enter the world of “The Sharpshooter Blues.”

It is an odd and oddly affecting world that Lewis Nordan has created in his five books of fiction. Arrow Catcher sits over to one side of the flat, story-haunted Mississippi Delta. Its citizens are lost in a time somewhere between the Civil War and last week. It might be the 1960s, since Nordan’s most recent and celebrated novel, “Wolf Whistle,” brought real-life events of those turbulent years home to Arrow Catcher. But “The Sharpshooter Blues” has an insistently dreamy quality, a sense of timelessness and isolation that borders on the fabulous.

In the lush opening description of the swamp, “rats the size of yellow dogs clung to the bark of trees and yapped like puppies and then dropped into the water and held their noses up above the flood and swam to high ground where they sat and howled at the moon by night.”

In this swamp lives large-headed, simple-minded Hydro, “about 20,” who peers into the cypress-stained water and dreams. Hydro would get along fine with Forrest Gump. He loves his daddy, Mr. Raney. He loves comic books, particularly Wonder Woman, Mr. Magoo, and Casper the Friendly Ghost, and he loves the wanted posters that the guy on the mail boat brings from the post office once a week. Also he loves his job at the William Tell market, where he dispenses bootleg whiskey along with gas in $1 and $2 amounts.

Hydro is having an excellent Sunday sitting around the William Tell with his pudgy 10-year-old buddy Louis, reading old issues of “Gerald McBoing Boing.” The other regulars include Leonard Reel, “an extra-fat melancholy man” who comes out to the William Tell every Sunday to confess the sins he has committed cruising truck-stop bathrooms the night before; Preacher Roe, who gets disgusted if Reel’s confession isn’t lurid enough; and Morgan, the sharpshooter of the title. Morgan is “tiny as a midget, almost. He was a foundling, got raised up by a hoodoo woman, and it stunted his growth.” Today he’s decided to have a little fun with his six-shooter and Hydro.

Soon we’re off in a field, and Morgan is trick-shooting watermelons off poor Hydro’s head. “Try not to shoot me in the head,” Hydro calls. You just know somebody’s going to get killed--miraculously, no one does. Hydro even gets a crack at the gun himself, and turns out to be a pretty smooth shot.

That’s a good thing, but it doesn’t stay good for long. Before the evening is over, the William Tell has been invaded by a couple of strangers with their own guns, a brother and sister, “lovely children,” dressed all in black. They have come for the bootlegger’s money, and when they’ve got it they mean to kill Hydro and be on their way--but not before the sister gets a crack at sex with the big-headed kid. Louis listens from a hiding-place. In a loony scene that’s like a cross between “Pulp Fiction” and “Ernest Goes to Camp,” the “lovely children” get what’s coming to them, and suddenly Hydro is a killer.

The trouble is, no one understands that. Everyone thinks Morgan must have shot the intruders, being a sharpshooter and all. “I wouldn’t worry too much about Morgan killing them two lovely children, if I was you,” Hydro’s father tells him, but of course Hydro does worry.

“I’ll live forever with the blood of them two lovely children on my hands,” he thinks, “and won’t nobody even let on that I done it.” It’s hard to say which is worse for him, having done the killing, or not getting the credit and the blame.

From this opening flourish, the novel spins out in several directions, some of which are more effective than others. Hydro tries to tell somebody what happened. No one listens. Louis, the pudgy eyewitness, points a finger at Morgan as the killer. Marshal Webber Chisholm, the only law in town, sets the wheels of injustice in motion. The town undertaker, known as “The Prince of Darkness,” gets into the act, although his purpose in the story never becomes quite clear. Hydro suffers, and broods; no one understands why.

The reader follows the big lie through the streets and houses of Arrow Catcher, watching it spread in an inverted ripple that is a mirror-image of the technique Gabriel Garcia-Marquez adopted in “Chronicle of a Death Foretold.” In that story, everyone knew a murder was going to take place but no one acted to stop it. In Nordan’s tale, a justifiable act of self-defense becomes a murder in the retelling, and the death that results is both tragic and inevitable.

Nordan is a very funny writer, and his stories are moving in a way that summary cannot convey. His characters are richly detailed and exceptionally sweet natured; they show their love in strange ways, but they show it. Hydro’s father is a wonderful character, bursting with love for his poor, big-headed boy. In the end, his grief is the force that brings all the story’s characters together, and rarely has sorrow been rendered in such smooth, even strokes. Lewis Nordan is not the kind of writer to forget that people tend to laugh when the pain is greatest.