“Since we’re going to have a baby,” said Molly, sitting on their living-room couch, “there’s something I want you to do.”

Pierre put down the remote control. “Oh?”

“I’ve never had anyone study my— my gift. But since we are going to have a child, I think maybe we should know some more about it. I don’t know if I want the child to be telepathic or not; part of me hopes it is, part of me hopes it isn’t. But if it does turn out to share my ability, I want to be able to warn him or her before it develops. I went through hell when it started happening to me when I turned thirteen — thought I was losing my mind.”

Pierre nodded. “I’ve certainly been curious about the science behind what you can do, but I didn’t want to pry.”

“And I love you for that. But we should know. There must be something different in my DNA. Can you find what it is?”

Pierre frowned. “It’s almost impossible to find the genetic cause of something with only one sample. If we knew of a large group of people who had your ability, we might be able to track down the gene responsible.

That’s how the Huntington’s gene was found, after all. They used blood samples from seventy-five families around the world that had Huntington’s sufferers. But with you being the world’s only known legitimate telepath, I don’t think there’s anything we can do in terms of looking for a gene.”

“Well,” said Molly, “if we can’t find it by working from the DNA up, what about reverse engineering? My guess is that there’s something chemically different in my brain — a neuro-transmitter, say, that no one else has, a chemical that perhaps allows me to use my brain’s neuronal wiring as a receiver. If we could isolate it and establish its amino-acid sequence, could you search my DNA for the code that specifies those amino acids?”

Pierre lifted his shoulders. “I suppose that might be possible, if it’s a protein-based neurotransmitter. But neither of us has the expertise to do that kind of work. We’d have to get someone else involved, to take the fluid samples and to separate out the neurotransmitters. And even then, it’s just a hunch that that’s the cause of your telepathy. Still,” he said, his voice taking on a faraway tone, “if we could identify the neurotransmitter, maybe someday they could synthesize it. Maybe all anyone needs to read minds is the right chemicals in the brain.”

But Molly was shaking her head. “I don’t mean to sound sexist,” she said, “but I’ve always suspected the only reason I’ve survived this long is because I’m a woman. I shudder to think what some testosterone-crazed male would do when he picked up offensive thoughts — probably kill everyone around him.” She brought her gaze back to meet Pierre’s. “No.

Maybe someday far in the future, humanity might be able to handle something like this. But not now; it’s not the right time.”

Pierre was setting up an electrophoresis gel when the phone in his lab rang for the third time that morning. He sighed, wheeled across the room on his chair, and picked up the handset. “Tardivel,” he snapped into the mouthpiece.

“Hi, Pierre. This is Jasmine Lucarelli, over in endocrinology.”

Pierre’s tone immediately warmed. “Oh, hi, Jasmine. Thanks so much for getting back to me.”

“Uh-huh. Listen — where did you say you got that fluid sample you sent over?”

Pierre hesitated slightly. “Ah, it was from a woman.”

“I’ve never quite seen anything like it. The specimen contained all the usual neurotransmitters — serotonin, acetylcholine, GABA, dopamine, and so on — but there was one protein in there I’d never seen before. Quite complex, too. I’m only assuming it’s a neurotransmitter because of its basic structure — choline is one of its chief constituents.”

“Have you worked out its full makeup?”

“Not personally,” said Dr. Lucarelli. “One of my grad students did it for me.”

“Can you send me a copy?”

“Sure. But I’d still like to know where this came from.”

Pierre exhaled. “It’s — it’s a prank, I think. A biochem student cobbled it together, trying to make a monkey out of his prof.”

“Shit,” said Lucarelli. “Kids today, eh?”

“Yeah. Anyway, thanks for looking at it. If you’d send me your notes on its chemical structure, I’d be grateful — I, ah, want to put a copy in the student’s file, in case he tries a stunt like this again.”

“Sure thing.”

“Thanks very much, Jasmine.”

“No problem.”

Pierre hung up the phone, his heart pounding.

Pierre had spent the last fourteen days studying the unusual neurotransmitter from Molly’s brain. Whether it was the key to her telepathy or just a by-product of it, he didn’t know. But the substance, despite its complexity, was just another protein, and like all proteins it was built up from amino acids. Pierre worked out the various sequences of DNA that could code for the creation of the most distinctive chain of aminos in the molecule. There were many possible combinations, because of codon synonyms, but he calculated them all. He then built up segments of RNA that would complement the various sequences of DNA he was searching for.

Pierre took a test tube full of Molly’s blood and used liquid nitrogen to freeze it to minus seventy degrees Celsius. That ruptured the cell membranes of the red corpuscles, but left the hardier white corpuscles intact. He then thawed the blood out, the ruptured reds dissolving into lightweight fragments.

Next, he spun the tube in a centrifuge at 1600 rpm. The millions of white corpuscles — the only large objects left in the blood sample now — were forced down to the end of the tube, forming a solid white pellet. He removed the pellet and soaked it for a couple of hours in a solution containing proteinase K, which digested the white corpuscles’ cell membranes and other proteins. He then introduced phenol and chloroform, which cleared away the protein debris in twenty minutes, then added ethanol, which over the next two hours precipitated out the delicate fibers of Molly’s purified DNA.

Pierre then worked on adding his special RNA segments to Molly’s DNA, and looked to see if they clamped on anywhere. It took over a hundred tries before he got lucky. It turned out that the sequence that coded for the production of the telepathy-related neurotransmitter was on the short arm of chromosome thirteen.

Pierre used his terminal to log on to GSDB — the Genome Sequence Database, which contained all the genetic sequences that had been mapped out by the hundreds of labs and universities worldwide working on decoding the human genome. He wanted to see what that part of chromosome thirteen looked like in normal people. Fortunately, the gene that occurred there had been sequenced in detail by the team at Leeds.

The normal value was CAT CAG GGT GTC CAT, but Molly’s specimen began TCA TCA GGG TGT CCA — completely different, which—$

No.

No, not completely different. Just shifted one place to the right, one nucleotide — a T, in this case — having been accidentally added in the copying of Molly’s DNA.

A frameshift mutation. Add or remove one nucleotide, and every genetic word from that point on is altered. Molly’s TCA TCA GGG TGT

CCA coded for the amino acids serine, serine, glycine, cysteine, and proline, whereas the standard CAT CAG GGT GTC CAT coded for histidine, glutamine, glycine, valine, and arginine; both chains had glycine in the middle because GGG and GGT were synonyms.

Frameshifts usually garbled everything, turning the genetic code into gibberish. Many human embryos spontaneously abort very early on, before their mothers even know they’re pregnant; frameshifts were a likely reason for many of those failures. But this one—$

A frameshift mutation that might cause telepathy.