And the shuddering vista was utterly gone, as though it had never been. No host of armed stoats, no labyrinth of crowded spaces and no impossible darkness—just the mail tracks in the pale, cold light.

Robed Mrs. Stig sagged, and although she had plainly just saved them all, she looked very, very tired and old. Her long hair was grey streaked with white, Lee noticed. She looked like she might be fifty or might be a hundred.

“You must go now,” she said.

“I thought that was the point,” Lee put in.

“Go. With your feet. No door here. No way out but walking.” Mrs. Stig sat on her heels, holding her knees. “I have isolated the branch for now.”

“Nothing comes in, nothing comes out,” Khan said, and the woman nodded tiredly.

“You…” Lee blinked. “You barricaded us off from them…?”

“I have isolated this place and time, maybe two days, there are no usable…”

“Interstitial fractures,” Khan filled in. “You let off a fucking reality grenade.”

Lee stared at the pair of them: barely a common language, certainly no shared scientific notation, but they understood each other.

“A fucking reality grenade,” Mrs. Stig echoed, without enjoyment. “Just so. Not good, for anything, for reality.”

At that point, Stig came back. He had a deep cut across one cheek, below the eye. It didn’t seem to bother him.

“Done,” he said.

He mumbled a collection of syllables to his fellow, who replied in kind.

Stig turned to them. “I will lead you. There are other ways out. Ways into your city.”

“And then what, love?” Khan asked. “What if they send the rat squad? Or just, you know, people, with guns?”

“You will keep moving. We will keep moving you.” He glowered at Lee as though it was all her fault up to and including the end of the universe. “And when we have more doors, we will bring you.”

Mrs. Stig muttered something, and Stig gave her a manic-looking grin, eyes wide. It was an expression Lee had no frame of reference for, but likely didn’t mean anything good.

Interlude: The Dead

Excerpt from Other Edens: Speculative Evolution and Intelligence by Professor Ruth Emerson of the University of California

There has been a shadow over all these timelines. Earth’s oldest children have all had to face the reaper, as life loses its gamble against geology and continental drift. Two hundred and fifty million years ago, on every timeline, across every Earth, the great dying came. This was the End-Permian Extinction Event.

In our past, the Permian was a time of great reptiles and reptile cousins. Not dinosaurs though; the vacuum left by their deaths will be one of the opportunities the terrible lizards exploit to start their long dominance over the globe. This Permian world is one of fin-backed pelycosaurs, crocodile ancestors, armoured and predatory amphibians. Not to mention reptiles already well on the road to becoming mammals, our own forebears.