Rietta, a grandaughter, dreams that Karl Wallenda comes to her.

"Vati!" she cries. "What are you doing here, Vait?" (The family called him "Vati"; he fell on March 22, at 73-crouched to the wire with his balancing pole, then the wind blew him off and he fell 120 feet past the balconies of the Condado and Flamboyan hotels in Puerto Rico, the glint of car tops rushing up and up . . .)

"He comes to me, he tells me everything's okay, we talk, he hugs me," says Rietta, who is 17 and tired; blond with a hard, cirucs-kid's face.

She is sitting in a cinder-block dressing room at the Capital Centre, staring at the floor, jigging her leg, laughing a rackety laugh. Out in the corridor, a trumpeter from the Circus America band practices "Begin the Beguine," never quite finishing it. In the arena, wires glint, a trapeze swings, tigers grumble in front of the empty seats. Rehearsal time: Circus America opens Christman night.

"Where I find satisfaction and peace is in obeying God," says Rietta's brother Ricky, who is 23, brown-haired, -eyed,-moustached. "I feel the Lord has told me to be here, as a service to my family. I've been working and doing Bible study for two years with Youth with a Mission. It took me six months to make this decision."

Ricky draws a tiny Bible from his breast pocket, and scans to I Timothy, Chapter 5, verse 4 reading aloud:

"But if any widow have children or nephews, let them learn first to shew piety at home, and to requite their parents: for that is good and acceptable before God."

His grandmother is a widow, since March; his mother since July 29, 1972, when Ricky's and Rietta's stepfather, Richard Guzman, fell 60 feet to his death in Wheeling. W. Va.

Now, Ricky and Rietta are "The Great Wallendas," a trade name owned by their grandmother. (Their last name is Bogino, and there are other wire-walking Wallendas, including one grand-nephew of Karl they're never even met.)

They're performing with Circus America. Amony other stunts, they'll do the chair- and-bicycle pyramid, 33 feet up, in which Karl Wallenda once fractured a vertebra-not to be confused with the seven-Wallenda pyramid which collapsed in Detroit in 1962 when Karl Wallenda's nephew, Dieter Shcepp, screamed, "I can't hold any longer!"

Dieter died, nephew Richard Faughn died, and son Mario was paralyzed for life.

Aunt Rietta fell from a sway pole a year later in Omaha-fell 60 feet and died. Ricky and Rietta's mother, Carla, took over the act.

"We don't have any enjoyment out of risking our lives, you know," Ricky says in a tone of patient combat against some whisper he must hear in the audiences."Do you enjoy risking your life on the beltway? Of course not. I'd like to do a study, as a matter of fact, I'd like to find out what the risks are in driving a car compared to working on the wire."

Why not use a net?

"My grandfather never wanted a net," says Rietta, staring at the floor. "I never liked a net. You get over-confident when you use a net, and that's when you make mistakes, when you get over-confident."

But even so, with a net . . .

"My grandfather's brother was killed in the 1930s when he fell in a net and bounced out," says Ricky.

There's no arguing. The Wallendas do not use nets. No matter that for those of us who care, another death would be almost an imposition, and for those who don't, merely a spectacle.

They've never even theorized about the best way to fall.

"There's no way to practice falling from 30 feet," Ricky says, and Rietta laughs again, shy and brassy at the same time.

"I plan to keep on doing the high-wire act all my life," says Rietta. "Because I want to. Nobody made us do it as kids. We had a two-foot wire in the backyard in Florida; we'd go out and play. I started walking it when I was three. Either you do it or you don't, there's no in between."

"We want to do something we're good at," says Ricky. "We're not scared of it. We don't think about dying."

"With a wire you have a respect," says Rietta. "You concentrate."

Two hours after the Karl she dreams of fell in Puerto Rico, Rietta walked the wire.

"I concentrated," she says, "until my feet hit the ground."

"Better say touched the ground," says Ricky.

The most frightening thought of all, to a layman, would be that as Karl fell after all those years (gripping his balancing pole all the way down to the hotel driveway, and act of faith), he might have despaired, realizing that it hadn't been worth it.

"Nooooooo," says Rietta, with a very old patience. She understands, even at 17, that people don't understand even the rudiments, the steel cable pressig up through the elkshkin sole of a white boot, the fact that you never tilt your body to balance, never even move the pole from side to side, but just stay rigid and tip the pole, a little up, a little down.

"I have a recurring dream, too," says Ricky. "I dream that the bears get out of their cages, usually it's Albert Rix's bears, the ones with Circus America here. I'm scared of them. They're trained, but they're not tame, people don't realize that. They chase me. I have to get away. I dream I climb up on the wire, I climb up on a crane, on anything, and I look down and I'm safe."