Julian squinted at the tiny font. His eyebrows slowly lifted as he took in the alternative details of what had happened to Elsinore Mallory, according to Lisa Pryor’s imagination. If he hadn’t seen Khan’s flat’s security footage, he’d now be wondering if Pryor hadn’t caused her friend’s disappearance.

“So we call her into the station with a professional on hand. I don’t want to end up on the wrong end of a discrimination claim because we came down hard on a schizophrenic, or whatever she might be.”

“She might just be lying,” Julian said stubbornly.

Lawrence gave him a level look. “Real convincing story she spun in there.”

He nodded reluctantly and checked his own phone, to see just how dull and time-wasting his missed meeting had been. The first message he opened almost had him through the roof of the car.

Despite the best efforts of the security services, Dr. Kay Amal Khan had slipped her minders and vanished.

Interlude: The Posticthyans

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

Each branching timeline brings us closer to our own. In this world, the sea scorpions are only a memory, the trilobites no more than shabby detritovores already reaching the end of their long run. We are not quite done with arthropods, but the open waters of these seas teem with fish that you can at least recognize as such, jaws and all.

Just as in the eurypterids’ timeline, there is something magical about the boundary between land and water that nurtures complexity. The shifting biomes, dry to wet, wet to dry, mean twice as many predators, twice as many kinds of prey. There are opportunities for forays inland or out to the open ocean. To adapt to the surf and shore is to shoulder more burdens than to commit wholly to either land or water.

At first, these particular fish are mere opportunists, mudskipper-like things encroaching on the fringes of salt forests. Here, masses of unchecked ferns, horsetails and lycophytes tower in lieu of the trees that have yet to evolve. Insect life draws the fish here, a wealth of protein-rich food—if only it can be brought down to the water to be devoured. Bulbous, froggy eyes adapt over tens of generations to see above the waterline as well as below it. Brains bulge with the strain of calculating spit trajectories to bring down dragonflies and knock cockroaches off overhanging fronds. The air proves a potent medium for competing males to boast and bellow in. They co-opt aquatic organs to produce terrestrial sounds that would be deafeningly loud to us but are muted and dull to their makers’ crude ears.

By the end of the Devonian the shores are lined with colonies of big, slick-skinned beasts like lumbering elephant seals. Monsters neither fish nor true amphibian, which seem at least half mouth. And those big heads hold big brains.