At first, they talked only of  Sanfilippo. “I said, you know, thank goodness it’s not autism,” Jenny said, so exuberantly that it took Marion a moment to register the joke. 

“We thought Danny might have autism,” Marion said. They sat in Jenny’s living room, an untouched fruit plate on the coffee table. 

“When you think about the chances,” Jenny said. Then they were both silent. 

“Tell me how you’ve been doing with all this,” Jenny said.

“It depends on the day. And the hour.” This was the vague response Marion had learned to use. 

“I had an actual panic attack after we first found out. I really did. I was out in the parking lot, and I just couldn’t breathe. Justin took me to the emergency room,” Jenny said. “Can you believe it? This was less than a year ago. The director of our preschool was still saying, ‘Nothing’s wrong. She’ll catch up.’ And most of the time I believed her.” Jenny spoke as if they knew each other. Marion nodded in response. 

“What I really wanted was just something to totally knock me out, but of course they couldn’t give me anything like that,” Jenny continued. “I was pregnant. So all they’d offer me was a low dose of Ativan. Justin was so surprised I took it. I told him, ‘I have no choice.’ ” Jenny waved her hands and laughed as she said this. “Because I’d never done any sort of drug before.” 

Marion remained silent. “Are you thinking about the trial?” Jenny asked. “Of course you are—how could you not be? We’re all thinking about it.” 

“I was,” Marion said. 

It was for the trial’s qualification testing that Marion, her husband, Nick, and her son, Danny, now five, had arrived in Boston from New York that morning. The trial was for a treatment that could reverse the course of Sanfilippo—a treatment so untested its name was a sequence of letters and numbers: JTJ141. For three years, the question of whether or not Danny would be able to receive this treatment had formed the central preoccupation of Marion’s life. 

“But remind me when Danny was diagnosed,” Jenny said.

“At two,” Marion said.

“That’s so early,” Jenny said. 

Marion explained that Danny’s pediatrician had an unlikely familiarity with Sanfilippo. He’d seen in Danny’s face, in his forehead and eyebrows, the fate Marion had later learned to see. “We agreed to do genetic testing. But we didn’t believe him at all,” Marion said. Nick had, in his comically exaggerated, unselfconscious manner, pointed to his own large forehead, his bushy eyebrows.

They’d gone to the hospital to receive the results. She’d seen the size of the group that had assembled to meet them—multiple pediatricians, a geneticist, a social worker—and known it was something horrible. Danny would progress for only a year or two more, they were told; then he’d regress. He would die just before adolescence, if not sooner, bedbound and silent, having lost, one by one, every ability he’d ever gained. 

“I said, ‘There’s nothing you can do?’ ” Marion said. 

“And they told you it was a matter of symptom management.”

“Yes,” Marion said. They were again silent. Marion wondered when it would no longer seem rude to leave. 

“But you thought they were wrong?” Jenny said. It was Jenny who’d set up this meeting, having found Marion’s email address online. Was it friendship she wanted? Nick thought so. “It would be good for you to go,” he’d said to Marion. Healthy for her to socialize—that’s what he’d meant. At moments, he spoke as if he were her caretaker. 

“Or soon you realized they were wrong?” Jenny said, prompting Marion again. 

“I started reading articles about Sanfilippo right away,” Marion finally said. At first, she’d had to spend most of her time looking up terms: enzyme, heparan sulfate, siRNA. But eventually she’d discovered Dr. Hoplock’s treatment, which had cured the mice to whom he’d administered it, and learned about the clinical trial he’d failed to fund. She’d dedicated herself entirely to raising the $2.5 million, quitting her job—she’d been a lawyer—and working days, nights, weekends, forgoing sleep. 

She’d never been extroverted, had always hated attention, had not even wanted birthday parties for herself. She was still surprised that she’d managed to raise the money. It had been like throwing herself into a freezing lake and withstanding it, swimming. She’d become, even, a public figure on a very minor scale, appearing on various talk shows. She was attractive, she knew, skinnier than she’d ever been. She could recognize the value of this: an attractive mother got more interviews than an ordinary one. 

“It’s a specially engineered virus,” she’d say, “which is injected directly into the brain, and it contains within it the DNA—” The host would usually cut her off around this point. 

“What you’re basically saying is that this is a miracle.”

“Yes,” Marion would respond. “Yes, this could really be a miracle.” It was enough to wear the face she wore, of sadness and of hope, to say “miracle,” “gene therapy,” “my son”—this was what the producers wanted. 

They were right. There was a complex scientific explanation, but, really, it was a miracle. Administered the treatment, Dr. Hoplock’s mice had risen and walked again. She imagined mice near death opening their eyes, lifting up their heads. Mice like those in the children’s books she’d read to Danny, in dresses and overalls, alive and happy at the end of the book. A miracle, just when she most needed it, just when it had seemed her son would certainly die.

Marion had gone silent again. She tried to rouse herself—she mentioned the talk shows.