“Yes,” I said, my heart suddenly sinking. I really didn’t like where this was going. “In the end, things got so bad you had to use a superweapon to destroy the whole universe, so the demons couldn’t use it as a base to invade other universes. I remember. I still have nightmares.”

“This is it,” said Janissary Jane. “The superweapon. The last resort. The Deplorable End.”

She held it out to me on the palm of a surprisingly steady hand. The weapon didn’t actually look like much, but then, the really nasty ones often don’t. The Deplorable End was just a flat silver box, dull and lifeless, with a red button on top. It barely filled Jane’s palm, but there was still . . . something about it. The more I looked at it, the more uneasy I felt, as though a large and dangerous animal had just entered the room. I studied the box carefully, and had enough sense not to try to touch it. The Armourer had come forward and was peering over my shoulder at it, breathing hard in his excitement.

“Now that is impressive,” he said. “You don’t see craft and workmanship like that often, these days. How many spatial dimensions has it got? I keep losing count. And the energy signatures are off the scale . . . You have got to let me get that down to the Armoury and take it apart.”

“No, Uncle Jack,” I said firmly.

“Oh come on, I’ve got this really cool hyper-hammer I’ve being dying to try out . . .”

“No, Uncle Jack! Have you stopped taking your medication again? Jane, what is that, exactly? What does it do?”

“Simple to operate,” she said, her voice dull and lifeless. Her eyes were drooping shut again as the last of her strength went out of her. “Just press the button, and . . . Boom.”

“No more tower?” I said hopefully.

“No more anything,” said Jane, blinking owlishly. “No more universe. And no, you don’t get a timer. The Deplorable End is a one-time-only deal. What I’ve got here is the original device, the prototype. We used a somewhat improved version to put an end to the demon war. What I’ve brought you is, therefore, technically speaking, untested. But it should work. No reason I know of why it shouldn’t.” She slowly lowered her hand, as though the awful thing squatting on her palm were getting heavier. “I stole this, from the Multiversal Mercenaries’ Black Museum. I had to kill a lot of people to get this to you, Eddie. Some of them were friends, once. But now I have closed the book and burned all my boats . . . I can never go back. So don’t you ever give me cause to regret this, Drood.”

“How does it work?” I said, because you have to say something.