Dog, Jessica had thought.

My God — what an ugly kid! her mother had thought.

Molly made it to the top floor and into the bedroom before she began to shake with anger. She sat on the edge of the bed, rocking her beautiful daughter back and forth in her arms.

Three months passed; it was now the middle of December.

Amanda, in a crib across the room, woke up a little after 3:00 a.m. and started crying. The sound awoke both Pierre and Molly. Molly went over to the padded chair by the window, and he watched quietly as she sat in the moonlight, breast-feeding his daughter. It was hard to imagine a more beautiful sight.

His left wrist started moving back and forth.

Molly put Amanda back down, kissed her forehead, and returned to their bed. Pierre could soon hear the regular sound of his wife’s breathing as she fell back to sleep. Pierre, though, was now wide awake. He tried to steady his left wrist by holding it with his right, but soon that one began to shake, too.

He thought back to the Huntington’s support-group meeting in San Francisco. All those people moving, shaking, dancing. All those people, like him. All those poor people…

We had a guy from your lab give a talk a couple of years ago. Big old bald guy. Can’t remember his name, but he won a Nobel Prize.

Burian Klimus had spoken to that group, and —$

Holy shit. Holy fucking shit.

Avi Meyer hadn’t proven it yet — indeed, might never be able to prove it, after half a century — but Klimus could very well be a Nazi.

Which meant he might very well be involved with the local neo-Nazi movement…

Neo-Nazis had certainly been responsible for the stabbing attempt on Pierre’s life and the shooting of Bryan Proctor, and, given the similarity of weapon, quite possibly for the murder of Joan Dawson.

Klimus had addressed the Huntington’s group, had likely met the three members of it who had been murdered.

Klimus worked day in and day out with Joan; surely he’d been aware of her incipient cataracts.

And Klimus knew that Pierre had some genetic disorder; Pierre himself had told him that in explaining why he and Molly wanted to use donated sperm.

Voluntary eugenics, Klimus had said to Pierre. I approve.

Could the old man have been trying to improve the gene pool? Weed out some Huntington’s sufferers, maybe a diabetic or two?

But no — no, that didn’t make sense.

Joan Dawson was way past menopause; although she had a grown daughter, she herself was incapable of making further contributions to the gene pool.

And Klimus knew that Pierre wasn’t going to breed.

But if not eugenics, then what?

An image came to his mind from out of the past, from the early 1980s: a drawing on the front page of Le Devoir.

Twelve dead babies.

Not eugenics.

Mercy — or, at least, someone’s version of it.

After all, the same thought had come to Pierre, too, unbidden, unwelcome, unfair, but there nonetheless: some of those with Huntington’s would be better off dead. And the same might be said for an old woman who lived alone and was about to lose her sight.

Pierre lay awake the rest of the night, shaking.

Pierre took the elevator up to the third floor of San Francisco police headquarters and walked down to the forensics lab. He knocked on the door, then let himself in. “Hello, Helen.”

Helen Kawabata looked up from behind her desk. She was wearing a spruce green suit today, jade rings, and emerald ear studs. She’d also changed her hair since Pierre had last seen her: it was still frosted blond, but she’d traded the pageboy for a shorter, punkier look. “Oh, hi, Pierre,” she said, rapid-fire. “Long time no see. Listen, thanks for that tour of your facilities. I really enjoyed it.”

“You’re welcome,” said Pierre. Every now and then, he tried to respond to a “thank you” with a California “uh-huh,” but he had never felt comfortable with it. Still, his smile was a bit sheepish. “I’m afraid I have another favor to ask.”

Helen’s smile faded just enough to convey that she felt the books were now balanced: she’d done him one favor, and he’d repaid it with lunch and a tour of LBNL. She did not look entirely ready to help him again.

“I went to a Huntington’s support-group meeting several months ago, here in San Francisco. They told me three people who belonged to their group had died in the last two years.”

“Well,” said Helen gently, “it is a fatal condition.”

“They didn’t die from Huntington’s. They were murdered.”

“Oh.”

“Would the police have done any special investigations of that?”

“Three people belonging to a single group getting killed? Sure, we’d have checked that out.”

“I’m the fourth, in a way.”

“Because you went to one meeting? What were you doing, giving a talk on genetics?”

“I have Huntington’s, Helen.”

“Oh.” She looked away. “I’m sorry. I’d…”

“You’d noticed my hands shaking when I gave you the tour of my lab.”

She nodded. “I — I’d thought you’d had too much to drink at lunch.” A pause. “I’m sorry.”

Pierre shrugged. “Me, too.”

“So you think somebody has something against Huntington’s sufferers?”

“It could be that, or…”

“Or what?”

“Well, I know this sounds crazy, but the person could actually think they’re doing the Huntington’s sufferers a favor.”

Helen’s thin eyebrows rose. “What?”

“There was a famous case in Toronto in the early 1980s. It was everywhere in the Canadian media. You know the Hospital for Sick Children?”

“Sure.”

“In 1980 and ‘81, a dozen babies were murdered in the hospital’s cardiac ward. They were all given overdoses of digoxin. A nurse named Susan Nelles was charged in the case, but she was exonerated. The case was never solved, but the most popular theory is that someone on the hospital’s staff was killing the babies out of a misguided sense of mercy.

They all had congenital heart conditions, and one might have concluded they were going to lead short, agony-filled lives anyway, so someone put them out of their misery.”

“And you think that’s what’s happening to the people in your Huntington’s group?”

“It’s one possibility.”

“But the guy who tried to kill you — what’s his name… ?”

“Hanratty. Chuck Hanratty.”

“Right. Wasn’t Hanratty a neo-Nazi? Hardly the type known for humanitarian gestures — if you could even call something like this humanitarian.”

“No, but he was doing the job on orders from somebody else.”

“I don’t remember seeing anything about that in the report on the case.”

“I — I’m just speculating.”

“Mercy killings,” said Helen, trying the idea on for size. “It’s an interesting angle.”

“And, well, I don’t think it’s just Huntington’s sufferers. Joan Dawson — she was the secretary for the Human Genome Center — was murdered, too. The police said the same kind of knife that was used in the attack on me was also used in killing her. She was an elderly diabetic, and she was going blind.”

“So you think your angel of mercy is offing anyone who is suffering because of a genetic disorder?”

‘Maybe.“

“But how would this person find out? Who would know about you and — what’s her name? — Joan?”

“Someone we both worked with — and someone who had also spoken to the Huntington’s group.”

“And is there such a person?”

“Yes.”

“Who?”

“I’d rather not say — not until I’m sure.”

“But—”

“How long do you keep tissue samples from autopsies?”

“Depends. Years, anyway. You know how court cases drag on. Why?”

“So you’d have samples from various unsolved murders committed in the last couple of years?”

“If an autopsy was ordered — we don’t always do one; they’re expensive.

And if the case is still unsolved. Sure, samples would still be around somewhere.”