The evidence of her mission can be found all over her house in Steventon, a picturesque village not far from Oxford. There she lives with four adopted sons, each with Down syndrome: James, 27; Otto, 21; Titus, 13; and Raphael, 5. People often say that such a family must make for a crazy household (for a while the boys were joined by their 85-year-old grandmother, who was struggling with dementia), but Baxter says that "ordinary people are much more difficult." She wants each of her sons to flourish in the way that's right for him, and she wants all of them to be exposed as much as possible to mainstream life.

Of the four, Otto stands out as Mr. Popularity. Although his face and his voice bear the obvious signs of Down syndrome, he can read and write, he can be fluid and witty in conversation, and he's wired like a frat boy, with a passion for Jackass, video games, fast food, classic rock, and beer. "He's always been incredibly outgoing," Lucy says. "He loves other people, and he wants to be in the middle of things. And that's been the thing—to try and keep him in the middle of things when the world is trying to put him off to one side. I brought Otto up to have no limits."

This limitlessness does not exclude sexuality, and that's exactly what seems to make people nervous. "The old myth is still alive and well that people with Down syndrome are 'eternal children'—they never really grow up," says Karin Melberg Schwier, the coauthor of Sexuality: Your Sons and Daughters With Intellectual Disabilities and the mother of an adult son with Down syndrome. "I still bristle every time I see the media referring to a 'child in an adult body.'"

Lucy Baxter's point is that her sons are free to make their own decisions; she says she has no intention of becoming Otto's sexual procurer. "I think it would be fairly sordid to go to a brothel," she says. "I wouldn't be all that happy about it. But if that's what Otto wanted to do, I would certainly not stop him. There is a big difference between what I would like and what Otto would like and what I believe Otto has the right to have. I've been speaking about the rights of disabled people—the fact that he has the right to choose—and I won't stop him in what he decides."

What she really wants for Otto, she says, is what any mother would want for her child—a refuge from loneliness, a person to share moments with, a partner. "I would love for him to have a girlfriend and a wife," she says. "And sex, as well, within that relationship. Just an ordinary fairy-tale relationship. It would make me happy because that's what would make him happy."


3.

"Hey, Bill," Otto says.

"Hmmm," Bill murmurs from the back seat of the car, where he's staring at rock formations.

"Do you think that all the girls from all the strip clubs will scream for me on the telly?" Otto has an ongoing love affair with the camera. Besides his TV appearances, he scored a leading role in the indie film Love and Kisses, a 10-minute excerpt of which screened at the 2008 Raindance film festival in London. He is smitten with the idea of becoming a movie star.

"They might," Bill says, "if they see you on TV."

This triggers an avalanche of imagined dialogue. "'Ahhhhh! There's Otto! I want to have sex! Come on, girls, let's find him! Ahhhh! We want to take his clothes off! Let's shag him! You take his shoes off! You take his socks off! You take his trousers! Girls, unbutton his shirt! Take everything off! Let's put his glasses on the table. Let's snog him, touch him, lick him . . . '"

"Otto," Bill intervenes, "don't you want to keep this inside your head? I don't want to hear all those things."

There is something about Otto and Bill's Route 66 bull sessions that calls to mind a running dialogue between the id and the super-ego, or maybe between the Marquis de Sade and Mister Rogers. Bill is a model of serenity and restraint, uttering barely a peep for miles. Otto is a one-man circus of burps, farts, howls, grunts, pranks, convoluted expressions of lust, snippets of rock anthems, scraps of action-movie dialogue, and hilarious but thoroughly inappropriate queries along the lines of "Are you gay?" and "Do you fancy Michael Jackson?" and "Does your wife have big boobies?" He has no filter. You might say he represents what a sizable majority of 21-year-old men would sound like if they had no filter.

"How long have you had sex with Holly?" Otto asks.

"Pardon?"

"How long have you had sex with Holly?"

"Do you mean how long does it last, or how long have we been doing it?"

"How long have you been doing it?" Otto clarifies.

"I'm not sure I want to answer that, Otto," Bill says. "You've been asking a lot of very personal questions."

Bill is by no means the only target of Otto's Tourettic play-by-play. Somewhere near the border between Arizona and Nevada we pull into a roadside diner called Rosie's. Within seconds of securing a stool at the counter, Otto has taken a fancy to a redhead who's dashing here and there in the kitchen.