THE FIRST THING THAT struck Samuel as he reached the icy-cold top floor was that he had suddenly developed two phobias: acrophobia, a dreadful fear of heights,⁶² swiftly followed by astrophobia, the fear of space. Samuel had never been frightened of heights before, and he had always been entranced by the immensity of space. He could spend a happy hour lying on his back in the garden at night, Boswell sleeping beside him, just watching the stars and feeling as though he were adrift among them.

But the top floor of Wreckit & Sons was a different matter entirely, in part because there was no longer really a floor there, or a ceiling. The memory of them remained, the faintest outline of boards beneath his feet and plasterwork above his head, but they resembled little more than chalk marks that were slowly being washed away by rain. Even as fear overtook him, Samuel wondered if this was what it was like to be a ghost: perhaps ghosts felt themselves to be real and substantial, and the world around them seemed pale and faded.

Beyond the near-vanished lines of the old store, and the fading shapes of trees, the Multiverse waited. It was a world of light and dark, of stars being born and stars dying, of clusters of swirling galaxies and gaseous columns of nebulae. Samuel could pick out the colors of the stars, shading from the blue of the new to the red of the old. He saw clouds of asteroids, and meteors turning to fire in the atmosphere of unknown worlds, and quasars, the brightest objects in the universe, their light powered by supermassive black holes. He saw universe layered upon universe, like panes of painted glass separated by distances simultaneously great and small. And he himself was both tiny and vast, for all that he saw seemed to revolve around him: he was suspended at the heart of the Multiverse.

The second thing that struck Samuel was a dwarf, as Angry, who had been leading the way, discovered that being a leader is only fun if you’re collecting a trophy, or a cash prize. It’s not fun if, as leader, you’re the first person to put a foot where you expect a floor to be, only to find that a large number of universes have opened up in its place, and it looks like a very long way down. He slammed painfully into Samuel’s stomach, knocking the air from Samuel with his elbow.

“Mind your step there,” said Angry. “There’s a bit of a drop.”

The others had paused on the stairs, aware that there was some problem ahead, but now the steps behind them began to vanish, one by one, as the lower floors of Wreckit & Sons turned to mist and were gone.

“The stairs are disappearing, Samuel,” shouted Maria. “We have to move up.”

But Samuel couldn’t budge. His feet were frozen in place on what little solidity remained. He willed them to move in order to make room for the others to join him, but he couldn’t. It was only then that he looked down and saw there was nothing beneath him after all but stars. He waited for himself to begin falling, like a character in a cartoon who manages to run off the edge of a cliff and but doesn’t start to drop until he realizes what he’s done, but Samuel did not fall, and he could definitely feel something solid under his shoes. Tentatively, he tapped with his toe. Whatever was beneath him felt like wood, and sounded like wood, which meant that it was, in all likelihood, wood.