There was a world where awareness came to the treetops. Small reptilian thinkers, somewhat like gliding monkeys, built complex nest villages in the high canopies. They traded jewel-shelled beetles and kept records of their dealings by stringing beads on vines. They painted themselves in gaudy colours and left votive offerings and ritual diagrams in deep caves. Here they braved huge centipedes and spiders to find a spiritual connection to the Earth. And yet the Earth betrayed them, and only their paintings and beads are left. In their case, chance factors intensified the hostile conditions of the dying times. Nothing larger than plankton was left in the sea, nothing but bacterial colonies were left on the land. It is a blow from which their Earth is still recovering, two hundred and fifty million years later.

And, because we are most affected by those most like ourselves, I will tell you of a timeline where our ancestors had their chance. Even as the world was turning to heat and poison, proto-mammals were evolving bigger brains and a bipedal posture, with only a stump of a tail left. They had hands more dextrous even than our own. They made tools from stone. They lived in nomadic troupes that bellowed and postured at one another when they met, and sometimes traded individuals or food. They were on the very cusp of intellect. Then the dying times crushed all their potential and left them in the dirt, and in the past. And though life went on for their Earth, they would never return.

The lesson here is that the Earth doesn’t care; that bad things happen; that it could so easily have been us. I have been describing worlds branching sequentially out of the earliest reaches of Earth’s history, but every timeline from here on in will diverge with one key advantage. The dying times are already behind them, as they are behind us.

8.

I

It took four police officers fifteen minutes’ hard work, even with a ram, to get into Alison’s apartment. Julian found this perversely reassuring, despite the situation. Had Alison been required to destroy evidence in her possession—if they had been the enemy, instead of the cavalry—the intruders would have broken in to find trashed computers and a bonfire of documents.

The difficult entrance also dispelled any hints from Royce and his people that Julian had suddenly turned hysterical about the disappearance of a colleague. Because the door had been thoroughly, almost absurdly, locked from the inside—and Alison was no longer in residence.

They stood in the entrance hall, looking through the empty doorway into the living room and kitchenette space. Taking every precaution, officers went into the bedroom in pairs. Julian heard them opening the wardrobe. And doubtless they were looking under the bed, too, into any space that might hide a human body, living or otherwise.