From within his suit of metal he withdrew yet more metal—the intersecting discs and dials of an astrolabe. I knew from school that astrolabes were used in the Middle Ages to identify stars. But none that I’d seen in textbooks measured up to this clockwork contraption. It was no larger than a teacup saucer but intricate beyond imagination. At least four rings, each pitted within the other, rolled about on sharp bronze teeth, while two hands notched with indecipherable measurements struck collision points. The whole thing was encased in a lattice of gold and decorated around the circumference with a forest silhouette so detailed that I could make out the etchings of individual leaves. Craftsmanship notwithstanding, the gold was burnished, the bronze stained, the various components bent and chipped.

Jack held the weathered astrolabe in the air, spun the wheels, and swept it across an increasingly small stretch of wall until he was able to touch one single brick with a finger. This was ARRRGH!!!’s signal. She shouldered her way closer, footfalls disrupting the TV signals. Several trolls broke from their trances and threw us spiteful looks.

ARRRGH!!! placed both paws to the wall. The muscled carpet of her back rippled and the wall opened along the irregular pattern of the brick. I covered my face against the specks of stone sent swirling by the churning cloud of dust. Tub and I shooed away the grit and watched as Jack and the two trolls made their way into a place that looked oddly familiar. We, too, passed through the door and were so amazed by what we saw that we weren’t startled by the sound of the wall sealing shut behind us.

A road sign. That’s what we were looking at. Not in troll language, not featuring some multiheaded beast, just a regular yellow road sign warning truck drivers that the bridge had a low clearance. Yes, that’s right—we were under a bridge. More specifically, a highway underpass in a darkened, industrial corridor in what looked like an anonymous suburb. We looked around and found worthless crap that now was the most welcome sight in the whole world: obscene graffiti on the concrete, six-pack rings collecting against a chain-link fence, and the red-and-yellow lights of a fast-food joint just over the next rise in the road. There were street signs, too, and Tub was excitedly pointing them out.

“De La Rosa! We’re in De La Rosa! We could walk home from here!” He addressed Jack. “Is it cool if we walk home from here?”

Jack was still consulting his astrolabe. Cars crossed overhead, oblivious of the creatures that lurked below. After an interminable silence, he snapped shut the golden device and pointed.

“Nullhullers. Two blocks away. They’re converging. We need to make this quick.”

He threw down the sack. I flinched at the violent clashing noise. Jack jabbed his chin at it.

“Go ahead.”