Pierre stared out the lab window, contemplating it all.

If a frameshift in a protected region occurred by accident due to a random addition or loss of a base pair from the chromosome, the cytosine-methylation checksum saw to it that any future copies — including those used in eggs or sperm — were corrected, preventing the error in coding from being passed on to the next generation. Molly’s parents had not been telepaths, nor was her sister, nor would any of her children be.

Pierre understood what it meant, but was still shocked. The implications were staggering: a built-in mechanism existed to correct frameshifts, a built-in way of keeping certain fully functional bits of the genetic code from becoming active.

Somehow, the enzymatic regulator had failed to work during the development of Molly’s own body. Perhaps that had been due to some drug — prescription or illegal — Molly’s mother had been using while pregnant with Molly, or to some nutrient missing from Molly’s mother’s diet. There were so many variables, and it was so long ago, that it would likely be impossible to duplicate the biochemical conditions under which Molly had developed between her conception and birth. But whatever had happened then had allowed the expression of something that was — the anthropomorphic language kept springing to Pierre’s mind, despite his efforts to avoid it — that was designed to remain hidden.

A Saturday afternoon in June. The doorbell rang.

“Who could that be?” said Pierre to little Amanda, who was sitting in his lap. “Who could that be?” He made his voice high and soft, the exaggerated tones generations of parents have used when talking to their babies. Meanwhile, Molly got up and went to the door. She checked the peephole, then opened the door, revealing Ingrid and Sven Lagerkvist, and their little boy, Erik.

“Look who’s here!” said Pierre, still baby-talking to Amanda. “Why, look who’s here! It’s Erik. See, it’s Erik.”

Amanda smiled.

Sven was carrying a large wrapped gift. He kissed Molly on the cheek, handed the gift to her, and came into the living room.

Molly placed the package on the pine coffee table. She then came over to Pierre and took Amanda from him. Although Pierre loved holding his daughter in his arms while sitting in a chair, he’d given up walking and carrying her after almost dropping her a few weeks before.

Molly carried Amanda into the middle of the room and set her down on the carpet near the coffee table. Sven, holding Erik’s chubby little hand, led him across the living room to where Amanda was.

“Manda,” said Erik in his soft, slurred way. As was typical of those with Down’s syndrome, Erik’s tongue stuck partway out of his mouth when he wasn’t speaking.

Amanda smiled and made a small sound low in her throat.

Pierre leaned back in his chair. He hated that sound, that little thrumming. Each time Amanda made it, his heart skipped. Maybe this time — maybe at last…

Molly pointed at the brightly wrapped box and spoke to Amanda. “Look what Erik and Uncle Sven and Aunt Ingrid brought for you,” she said.

“Look! A present for the birthday girl.” She turned to the adult Lagerkvists. “Thanks so much, guys. We really appreciate you coming over.”

“Oh, it’s our pleasure,” said Ingrid. She was wearing her red hair loose about her shoulders. “Erik and Amanda always seem to have such a good time together.”

Pierre looked away. Erik was two; Amanda was one. Normally, they wouldn’t have made good playmates, but Erik’s Down’s syndrome had already held up his mental development enough that he really was at much the same stage as Amanda.

“Would either of you care for coffee?” asked Pierre, meticulously rising from his chair, then holding on to its back until he was completely steady.

“Love some,” said Sven.

“Please,” said Ingrid.

Pierre nodded. They’d gotten past the point, thank God, where Ingrid insisted on offering to help Pierre with every little thing. He could manage making coffee — although he would need someone else to carry the steaming cups back to the living room.

He poured ground coffee into the coffeemaker. Next to the machine sat the cake Molly had bought, a Flintstones birthday cake crowned with plastic figures of Fred and Wilma surrounding a baby Pebbles; Molly had said there had been a Barney/ Betty/Bamm Bamm version for little boys.

Red lettering on the white frosting said “Happy First Birthday, Amanda.”

Pierre resisted the urge to sneak a bit of the icing. He added water to the coffeemaker, then headed back into the living room.

The unopened gift had been set aside; they’d wait till after the cake for that. Erik and Amanda were now playing with two of Amanda’s favorite plush toys, a pink elephant and a blue rhinoceros.

Molly smiled up at Pierre as he came in. “They’re so cute together,” she said.

Pierre nodded and tried to return the smile. Erik was a well-behaved little boy; he seemed to be passing calmly through what for a normal child would have been the Terrible Twos. But, then, they knew exactly what was wrong with Erik. It was tearing Pierre up not knowing what was wrong with Amanda. After an entire year of life, she hadn’t said so much as “Mama” or “Dada.” There was no doubt that Amanda was a bright girl, and no doubt that she seemed to understand spoken language, but she wasn’t using it herself. It was both heart-wrenching and puzzling. Of course, many children didn’t speak until after their first birthday. But, well, Molly’s biological father was a certified genius and her mother was a Ph.D. in psychology; surely she should be on the fast end of the developmental cycle, and—$

No, dammit. This was a party — hardly the occasion to be dwelling on such things. Pierre returned to the living room.

Ingrid, on the couch, gestured at Erik and Amanda. “The time goes by so quickly,” she said. “Before we know it, they’ll be grown.”

“We’re all getting older,” said Sven. He’d been cleaning his Ben Franklin glasses on the hem of his safari shirt. “Of course.” he said, replacing them on his nose, “I’ve felt old ever since the girls in Playboy started being younger than me.”

Pierre smiled. “What did it for me was Partridge Family reruns. When I first encountered that show in the mid-seventies, I thought Susan Dey was the hot one. But I saw a rerun recently, and she’s just a skinny kid.

Now I can’t take my eyes off Shirley Jones.”

Laughter.

“I knew that I was getting old,” said Molly, “when I found my first gray hair.”

Sven waved his arm dismissively. “Gray hair is nothing,” he said; there were more than a few in his massive beard. “Now, gray pubic hair…”

The doorbell rang again. Pierre went to open it this time. Burian Klimus stood on the stoop, his ever-present pocket notebook visible in his breast pocket.

“I hope I’m not too late,” said the old man.

Pierre smiled without warmth. He had hoped that his boss had been kidding about wanting to come over for the baby’s birthday. Klimus kept finding reasons to visit Molly and Pierre at home, kept looking at little Amanda, kept writing things in his notebook. Pierre wanted to tell him to go to hell, but he still wasn’t permanently assigned to LBNL. Sighing, he stood aside and let Klimus come in.

Everyone had gone home. The cake had been devoured, but the cardboard tray it had come on still sat on the dining-room table, a ring of frosting and crumbs on its upper surface. Empty wineglasses were perched on various pieces of furniture and on one of the stereo speakers.

They’d clean it up later; for now, Pierre just wanted to sit on the couch and relax, his arm around his wife’s shoulders. Little Amanda sat in Molly’s lap, and with her chubby left hand was holding on to one of her father’s fingers.