Professor Stefan was right: the Large Hadron Collider had worn thin the walls between dimensions, and the pickax jabs of the detection experiments had done the rest. A hole had been opened, and now the Shadows were about to pour through. The Great Malevolence might have wanted to destroy humanity and burn worlds. It might have wanted misery and ruin. But it also wanted the Multiverse to remain in existence. It wanted to transform universes into branch offices of Hell, and to do that required the continued survival of the Multiverse.

The Shadows wanted only nothingness. They were as much a danger to the Great Malevolence as they were to humanity. This was why Crudford, after a quick return visit to Hell, had come down to Earth. He now believed that he knew why Biddlecombe was the place to which the Shadows had come. Mrs. Abernathy’s heart had hidden itself on Earth, and its blackness had found an echo in the Kingdom of Shadows. She had called out to the Shadows, and an alliance had been formed. She would give the Earth, and then the Multiverse, to the Shadows.

And in return, they would give Samuel Johnson to her.

50. Although unfortunately not Mr. Tuppenny the ice cream man.

51. He did all that in a paragraph. It took me two books. I’m in the wrong business.

52. So how big is the Multiverse, exactly? According to quantum theory, particles can pop into and out of existence, and there are scientists who believe that our universe was the result of just such a quantum “pop.” So if one universe can pop into being, why not many universes? This would require extra dimensions, which is where very complicated string theory comes into play. String theory proposes that our universe is made up of very, very small vibrating strings, and when the strings vibrate in different ways they produce different particles. Think of the strings of a guitar producing different notes, and so the universe can be imagined as a great symphony of particles being produced by an unseen orchestra. Pluck one string and you get a proton; pluck another and you get an electron.

One of the difficulties in understanding string theory lies in the fact that it doesn’t work in our four-dimensional world (the three space dimensions of up/down, left/right, and forward/backward, and the fourth dimension of time). String theory requires eleven dimensions, ten of space—which are buried within our existing three dimensions—and one of time. One of the tasks of the Large Hadron Collider was to find proof of these extra dimensions: if, during the Collider’s proton collisions, some of the bits of shattered particles were found to have gone missing from the sealed vacuum, then that would suggest the possibility that they had disappeared into other dimensions.

Anyway, to get back to our original question of how many universes there may be in the Multiverse, some string theorists suggest the number is 10⁵⁰⁰, or one for every possible model of physics that string theory offers. (See, I told you it was complicated. It’s so complicated that this latest version of string theory, the eleven-dimension one, is known as M-theory, and even Edward Whitten, the man who came up with it, isn’t sure what the M stands for.) Mind you, there are some scientists who say that the number of universes in the Multiverse could be far more than 10⁵⁰⁰, and that the only way you can get it down to 10⁵⁰⁰ is by fiddling about with the (coarse) Moduli Space of Kähler and Ricci-Flat (or Calabi-Yau) metrics and then enforcing extra-supersymmetry conditions, which is just cheating, obviously. I mean, everybody knows that.