“Let Mama see.” With a little difficulty, Brianna succeeded in getting her fingers onto the rock, though Jemmy wouldn’t surrender it. “It’s warm,” she said, looking up. “Like the piece of opal—but not way hot. If it gets way hot, you drop it fast, OK?” she said to Jemmy.

Roger had been watching this with fascination.

“He’s got it, hasn’t he?” he said softly. “Fifty/fifty, you said, or three chances in four, depending—but he’s got it, doesn’t he?”

“What?” Jamie glanced at Roger, then me, one red brow raised in question.

“I think he can . . . travel,” I said, feeling a tightening of my chest at the thought. “You know what Otter-Tooth said—” I nodded at the journal, which lay discarded on the desk. “He said they had to take a test—to see if they could hear ‘the voice of time.’ We know that not everyone can . . . do this.” I felt unaccountably shy, talking of it before Ian. “But some can. From what Otter-Tooth said, there was a way of finding out who could and couldn’t, ahead of time, without having actually to try.”

Jemmy was paying no attention to the grown-up conversation, instead rocking back and forth, humming to the stone clutched in his pudgy hand.

“Do you suppose the ‘voice of time’ is—Jem, can you hear the rock?” Roger leaned forward, taking hold of Jemmy’s arm to compel his attention away from the emerald. “Jem, is the rock singing to you?”

Jemmy looked up, surprised.

“No,” he said uncertainly. Then, “Yes.” He held the rock up to his ear, frowning, then thrust it at Roger. “You sing, Daddy!”

Roger accepted the emerald gingerly, smiling at Jemmy.

“I don’t know any rock songs,” he said, in his husky rasp of a voice. “Unless ye count the Beatles.” He lifted the rock to his own ear, looking self-conscious. He listened intently, frowning, then lowered his hand, shaking his head.

“It’s not—I can’t—I couldna really say I hear anything. And yet—here, you try.” He passed the stone to Brianna, and she in turn to me. Neither of us heard anything in particular, and yet I thought I could perceive something, if I listened very hard. Not exactly a sound, more a sense of very, very faint vibration.

“What is it?” Ian asked. He had been following the proceedings with rapt interest. “Ye’re no sìdheanach, the three of ye—but why is it you can do . . . what ye do, and Uncle Jamie and I canna? Ye can’t, can ye, Uncle Jamie?” he asked dubiously.

“No, thank God,” his uncle replied.

“It’s genetic, isn’t it?” Brianna asked, looking up. “It has to be.”

Jamie and Ian looked wary at the unfamiliar term.

“Genetic?” Ian asked. His feathery brows drew together in puzzlement.

“Why shouldn’t it be?” I said. “Everything else is—blood type, eye color.”

“But everyone has eyes and blood, Sassenach,” Jamie objected. “Whatever color his eyes may be, everyone can see. This—” He waved at the small collection of stones.

I sighed with impatience.

“Yes, but there are other things that are genetic—everything, if you come right down to it! Look—” I turned to him and stuck out my tongue. Jamie blinked, and Brianna giggled at his expression.

Disregarding this, I pulled in my tongue and put it out again, this time with the edges rolled up into a cylinder.

“What about that?” I asked, popping it back in. “Can you do that?”

Jamie looked amused.

“Of course I can.” He stuck out a rolled tongue and wiggled it, demonstrating, then pulled it back. “Everyone can do that, surely? Ian?”

“Oh, aye, of course.” Ian obligingly demonstrated. “Anyone can.”

“I can’t,” said Brianna. Jamie stared at her, taken aback.

“What d’ye mean ye can’t?”

“Bleah.” She stuck out a flat tongue and waggled it from side to side. “I can’t.”

“Of course ye can.” Jamie frowned. “Here, it’s simple, lass—anyone can do it!” He stuck out his own tongue again, rolling and unrolling it like a paternal anteater, anxiously encouraging its offspring toward an appetizing mass of insects. He glanced at Roger, brows lifted.

“You’d think so, wouldn’t you?” Roger said ruefully. He stuck out his own tongue, flat. “Bleah.”

“See?” I said triumphantly. “Some people can roll their tongues, and some simply can’t. It can’t be learned. You’re born with it, or you’re not.”

Jamie looked from Bree to Roger and back, frowning, then turned to me.

“Allowing for the moment that ye may be right—why can the lass not do it, if you and I both can? Ye did assure me she’s my daughter, aye?”

“She is most assuredly your daughter,” I said. “As anyone with eyes in their head could tell you.” He glanced at Brianna, taking in her lean height and mass of ruddy hair. She smiled at him, blue eyes creasing into triangles. He smiled back and turned to me, shrugging in good-natured capitulation.

“Well, I shall take your word for it, Sassenach, as an honorable woman. But the tongue, then?” He rolled his own again, in doubtful fashion, still not quite believing that anyone couldn’t do it if they put their mind to it.

“Well, you do know where babies come from,” I began. “The egg and the . . .”

“I do,” he said, with a noticeable edge to his voice. The tips of his ears turned slightly pink.

“I mean, it takes something from the mother and something from the father.” I could feel my own cheeks pinken slightly, but carried on gamely. “Sometimes the father’s influence is more visible than the mother’s; sometimes the other way round—but both . . . er . . . influences are still there. We call them genes—the things babies get from their two parents that affect the child’s appearance and abilities.”

Jamie glanced at Jemmy, who was humming again, engaged in trying to balance one gemstone on top of another, the sunlight glinting off his coppery hair. Looking back, he caught Roger’s eye, and quickly turned his attention to me.

“Aye, so?”

“Well, genes affect more than simply hair or eye-color. Now,” I warmed to my lecture, “each person has two genes for every trait—one from the father, one from the mother. And when the . . er . . gametes are formed in the ovaries and testes—”

“Perhaps ye should tell me all about it later, Sassenach,” Jamie interrupted, with a sidelong glance at Brianna. Evidently he didn’t think the word “testes” suitable for his daughter’s ears; his own were blazing.

“It’s all right, Da. I know where babies come from,” Bree assured him, grinning.

“Well, then,” I said, taking back command of the conversation. “You have a pair of genes for each trait, one gene from your mother and one gene from your father—but when the time comes to pass these on to your own offspring, you can only pass one of the pair. Because the child will get another gene from his other parent, you see?” I raised an eyebrow at Jamie and Roger, who nodded in unison, as though hypnotized.

“Right. Well, then. Some genes are said to be dominant, and others recessive. If a person has a dominant gene, then that’s the one that will be expressed—will be visible. They may have another gene that’s recessive and so you don’t see it—but it can still be passed to the offspring.”

My collective audience looked wary.

“Surely you learned this in school, Roger?” Bree asked, amused.

“Well, I did,” he muttered, “but I think perhaps I wasna paying proper attention at the time. After all, I wasn’t expecting it actually to matter.”

“Right,” I said dryly. “Well, then. You and I, Jamie, evidently each have one of the dominant genes that allows us to roll our tongues. But—” I continued, raising a finger, “we must also each have a recessive gene, that doesn’t allow tongue-rolling. And evidently, each of us gave the recessive gene to Bree. Therefore, she can’t roll her tongue. Likewise, Roger must have two copies of the non-rolling recessive gene, since if he had even one of the dominant genes, he could do it—and he can’t. Q.E.D.” I bowed.

“Wat’s tes-tees?” inquired a small voice. Jemmy had abandoned his rocks and was looking up at me in profound interest.

“Er . . .” I said. I glanced round the room in search of aid.

“That’s Latin for your balls, lad,” Roger said gravely, suppressing a grin.

Jemmy looked quite interested at that.

“I gots balls? W’ere I gots balls?”

“Er . . .” said Roger, and glanced at Jamie.

“Mmphm,” said Jamie, and looked at the ceiling.

“Well, ye do have a kilt on, Uncle Jamie,” Ian said, grinning. Jamie gave his nephew a look of gross betrayal, but before he could move, Roger had leaned forward and cupped Jemmy gently between the legs.

“Just there, a bhalaich,” he said.

Jemmy kneaded his crotch briefly, then looked at Roger, small strawberry brows knitted into a puzzled frown.

“Nots a ball. ’Sa willy!”

Jamie sighed deeply and got up. He jerked his head at Roger, then reached down and took Jemmy’s hand.

“Aye, all right. Come outside with me and your Da, we’ll show ye.”

Bree’s face was the exact shade of her hair, and her shoulders shook briefly. Roger, also suspiciously pink about the cheeks, had opened the door and stood aside for Jamie and Jem to go through.

I didn’t think Jamie paused to think about it; seized by impulse, he turned to Jemmy, rolling up his tongue into a cylinder and sticking it out.

“Can you do that, a ruaidh?” he asked, pulling it back in again.

Brianna drew in her breath with a sound like a startled duck, and froze. Roger froze, too, his eyes resting on Jemmy as though the little boy were an explosive device, primed to go off like the opal.

A second too late, Jamie realized, and his cheeks went pale.

“Damn,” he said, very quietly under his breath.

Jemmy’s eyes grew round with reproach.

“Bad, Granda! At’sa bad word. Mama?”

“Yes,” Brianna said, narrowed eyes on Jamie. “We’ll have to wash Grand-da’s mouth out with soap, won’t we?”

He looked very much as though he had already swallowed a good mouthful of soap, and lye-soap, at that.

“Aye,” he said, and cleared his throat. The flush had faded entirely from his face. “Aye, that was verra wicked of me, Jeremiah. I must beg pardon o’ the ladies.” He bowed, very formally, to me and Brianna. “Je suis navré, Madames. Et Monsieur,” he added softly to Roger. Roger nodded very slightly. His eyes were still on Jemmy, but his lids were lowered and his face carefully blank.

Jemmy’s own round face assumed the expression of beatific delight that he wore whenever French was spoken near him, and—as Jamie had clearly intended—broke immediately into his own pet contribution to that language of art and chivalry.