The changeling had seen Mr. Berry in a bathing suit, so about 90 percent of its simulation was accurate. The other 10 percent might have made Mrs. Berry faint.

Similarly, the changeling could, in the dark privacy of Jimmy’s bedroom, discard an arm and most of a leg and make itself a piece of flesh that had a shape similar to that of the nurse Deborah, at least the form she apparently had under her uniform, severely corseted. But it had no more detail than a department store dummy. The times being what they were, it could have had free rein of the house and not found any representation of a nude female.

It was still months away from being able to simulate anything like social graces, but to satisfy this particular desire, no grace was needed. Precisely at 7:30, Deborah brought in the breakfast tray.

“Please take off your clothes,” it said, “and put them on the dresser.”

Deborah may or may not have recognized the doctor’s voice. She managed not to drop the tray. “Jimmy! Don’t be silly!”

“Please,” Jimmy said, smiling, as she positioned the lap tray. “I would like that very much.”

“So would I,” she whispered, and glanced back to see that the door was almost shut. “How about tonight? After dark?”

“I can see in the dark,” it said in her whisper, husky. She slid her hand into his pajamas, and when she touched the penis an unused circuit closed, and it enlarged and rose with literally inhuman speed.

“Oh my God,” she said. “Midnight?”

“Midnight,” it repeated. “Oh my God.”

Her smile was a cross between openmouthed astonishment and a leer. “You’re strange, Jimmy.” She backed out of the room, mouthing “midnight,” and closed the door quietly.

The changeling noted this new erect state and experimented with it, and the unexpected result suddenly clarified a whole class of mammalian behavior it had witnessed with porpoise, dolphin, and killer whale.

The music teacher came for his twice-weekly visit, and was stupefied by the sudden change in Jimmy’s ability. The boy had been a mystery from the start: before the accident, he had taken piano lessons from age ten to thirteen, the teacher was told, but had quit out of frustration, boredom, and puberty. Or so the parents thought. He must have been practicing secretly.

This current teacher, Jefferson Sheffield, had been hired on Dr. Grossbaum’s recommendation. His specialty was music for therapy, and under his patient tutelage many mentally ill and retarded people had found a measure of peace and grace.

Jimmy’s performance on the piano had been like his idiot-savant talent with language: he could repeat anything Sheffield did, note for note. Left to his own devices, he would either not play or reproduce one of Sheffield’s lessons with perfect fidelity.

This morning it improvised. It sat down and started playing with what appeared to be feeling, making up things that used the lessons as raw material, but transposed and inverted them, and linked them with interesting cadenzas and inventive chord changes.

He played for exactly one hour and stopped, for the first time looking up from the keyboard. Sheffield and most of the family and staff were sitting or standing around, amazed.

“I had to understand something,” it said to no one in particular. But then it gave Deborah a look that made her tremble.

Dr. Grossbaum joined Sheffield and the family for lunch. The changeling realized it had done something seriously wrong, and retreated into itself.

“You’ve done something wonderful, son,” Sheffield said. It looked at him and nodded, usually a safe course of action. “What caused the breakthrough?” It nodded again, and shrugged, in response to the interrogative tone.

“You said that you had to understand something,” he said.

“Yes,” it said, and into the silence: “I had to understand something.” It shook its head, as if to clear it. “I had to learn something.”

“That’s progress,” Grossbaum said. “Verb substitution.”

“I had to find something,” it said. “I had to be something. I had to be some… one.”

“Playing music let you be someone different?” Grossbaum said.

“Someone different,” it repeated, studying the air over Grossbaum’s head. “Make… made. Made me someone different.”

“Music made you someone different,” Sheffield said with excitement.

It considered this. It understood the semantic structure of the statement, and knew that it was wrong. It knew that what made it different was new knowledge about that unnamed part of its body, how it would stiffen and leak something new. But it knew that humans acted mysteriously about that part, and so decided not to demonstrate its new knowledge, even though the part was stiff again.

It saw that Grossbaum was looking at that part, and reduced blood flow, to make it less prominent. But he had noticed; his eyebrow went up a fraction of an inch. “It’s not all music,” he said, “is it?”

“It’s all music,” the changeling said.

“I don’t understand.”

“You don’t understand,” the changeling looked at its hands. “It’s all music.”

“Life is all music,” Sheffield said. The changeling looked at him and nodded. Then it rose and crossed the room to the piano, and started playing, which seemed safer than talking.

It was awake at midnight, when the door eased open. Deborah closed it silently behind her and padded on bare feet to the bed. She was wearing oversized men’s pajamas.

“You have clothes,” it said.

“I just got up to get a glass of milk,” she said, confusing it. The fluid it produced that way was not milk, and to fill a glass would take all night.

She read its expression almost correctly and smiled. “In case I get caught, silly.”

A little moonlight filtered through the curtains. The changeling adjusted its irises and made it bright as day, watching her slowly unbutton the pajama top.

It noted the actual size and disposition of breasts, not the way they appeared when she was clothed. The pigmentation and placement of nipples and aureoles. (It had wondered about its own nipples, which seemed to have no function.)

She slipped into bed next to it, and it attempted to pull down the pajama bottoms.

“Naughty, naughty.” She kissed it on the mouth and moved one of its hands to a breast.

The kiss was odd, but it was something it had seen, and returned with a little force.

“Oh my,” she whispered. “You’re hot.” She reached down and stroked the part that had no name. “Aren’t you the cat’s pajamas.”

That was pretty confusing. “No, I’m not.”

“Just a saying.” It moved both hands over her body, studying, measuring. Most of it was similar to the male body it inhabited, but the differences were interesting.

“Oh,” she said. “More.” It was studying the place that was most different. Deborah began to excrete fluid there. It went deeper. She moaned and rubbed its hand with the wet tissues there.

She closed her hand over the unnamed part, and stroked it softly. It wondered whether it was an appropriate time to leak fluid itself, and began to.

“Oh no,” she said; “oh my.” She shucked off her pajama bottoms and slid up his body to clasp him there, with her own wet parts, and move up and down.

It was an extraordinary sensation, similar to what he had done alone earlier, but much more intense. It allowed the body’s reflexes to take over, and they pounded together perhaps a dozen times, and then its body totally concentrated on that part, galvanized, and explosively excreted—three, four, five times, the pressure decreasing.

It breathed hard into the space between her breasts. She slid down to join her mouth with its. She inserted her tongue, which was probably not an offering of food. It reciprocated.

She rolled over onto her back, breathing hard. “Glad you remember something.”