“‘Ley line’ is kind of an informal term, but … you know that the earth’s crust is magnetic, right?”

“I can’t say I did, but I’m willing to take your word for it.”

“You may. And you do know that magnets are directional? Did you play with them as a kid?”

“You mean, positive end, negative end, and if you put the positive ends of two magnets together, they bounce apart? Yes, but what’s that got to do with ley lines?”

“That’s what a ley line is,” she said patiently. “The electromagnetism in the earth runs in parallel bands, and the bands alternate in the direction of their magnetic current. Though it’s not totally neat and tidy, of course. They diverge and overlap and like that. Haven’t I told you this stuff before?”

“Possibly.” He abandoned his half-formed amorous intentions, with a sense of regret. “But the ley lines I know about are … I don’t know what you’d call them, in terms of classification. Folklore, ancient builder stuff? At least in the British Isles, if you go looking at ancient hill forts and churches that are probably built on much older sites of worship and … well, things like standing stones, you often find that you can draw a straight—very straight, in most cases, as though it had been surveyed—line through two or three or four such sites. Archaeologists call those ley lines—though some folk call them spirit walks, because the dead are thought to … Oh, my God.”

A brief, uncontrollable shudder ran through him.

“Goose walking on your grave?” she asked, sympathy slightly marred by a look of satisfaction.

“Not everybody makes it,” he said, ignoring both sympathy and smugness. He pushed back the covers and sat up. “Through the stones. That’s what you mean? That the people who don’t go through, or don’t go through properly, turn up dead on these ley lines, leading to the not-unreasonable supposition that there’s something supernatural going on.”

“I hadn’t heard of spirit walks,” she admitted. “So I can’t say that’s what I mean—but it makes sense, doesn’t it?” She didn’t wait for him to admit it, but went on with her own line of thought.

“So … I’m thinking that the … time places … are maybe spots where different ley lines converge. If so, what happens to the electromagnetism in that spot would be really interesting, and it might be what … makes time be accessible? I mean, Einstein’s Unified Field Theory—”

“Let’s leave Albert out of it,” he said hastily. “At least for now.”