“But what has the old man been doing with you all this time if he’s taught you nothing at all? Weak spots on the earth and in the sky, bunny. The places where things get lost, and things get out. Places where things can slip through. Holes, from this side into the other, and vicey-versy. Into the Elsewhere!” She barked out a deep, booming man’s cry, like a circus ringleader introducing his greatest act: “The Great Beeeyond!”

Throwing her arms wide, she made a pirouette, before continuing in her own voice. “Get the gist? The Black Forest’s riddled with holes. German woods are like Swiss cheese. And you’re standing at the thinnest spot of all. Or you will be in a few minutes,” she added, checking the sky again, “when everything all lines up.

“This old castle was built around the weak spot by some little scared people. To keep it secret and keep all the happy peasants safe and stupid. Why else build anything in such a dreary dull nothingy place? But once upon a time, a very wise and very powerful man realized this spot was particularly special, and so he and his men took over the castle and settled in so he could examine it properly.

“So. He settled in with his old books and stuff and got all comfy and studied the weak spot for years and years and years. And here’s what he found. Most weak places are one way. Either things can go in, or things can get out. Like Hamelin. You must know that one, bunny?”

“Hamelin,” Alex said, reluctantly. He knew the name from the fairy tale that had always creeped him out most as a kid. “The town from the Pied Piper?”

“The town from the Pied Piper?” Zia repeated in a maddeningly exact imitation of his voice. “Yes. Go through that door in Hamelin, and it’s bye-bye, little kiddiewinks. See? But this one, this one’s so very, very close to the next one that when it all lines up”—she pointed to the sky—“they become two sides of one. One door. One gateway. Right here is one side, and it’s a way in. Now, big test, see if you’ve been paying attention. Can you guess where the other weak spot is? Where the other side comes out? Here’s a clue: this comes from there.” She tossed the rock in her hand.

“The mountain,” Alex said after a moment. “The Kandel.”

“By George, I think he’s got it!”

“No,” Alex said. “I don’t. I don’t get any of it.”

“Suffering catfish on a bike,” Zia said with an exasperated sigh.

“I . . . I’d like to know,” Alex said, quietly, as if he didn’t want anyone to hear him admit it. He kept his eyes down, studying the ground, their feet. “I’d like to understand.”