As she disappeared from view he cursed silently. Then he started down the passage, red dust tickling his feet. He would follow her out and explain everything, confess to the poisoning, put his plan at her mercy. Maybe she’d treat his desire to create the message as a kind of empty vanity and refuse to be a part of it, lest his deceit undermined the impact of the find. But he couldn’t be a helpless spectator, merely watching the mountain’s history unfold. She’d understand that, surely?

He stood at the entrance to the front cabin. Tarquinia had gone out – but he suddenly remembered that he’d never brought the tent-lever back into the Surveyor. He’d left it by the airlock outside. She’d been carrying something else, something similar in appearance.

He heard Agata humming with pain as the spasms in her gut failed to dislodge the tainted meal. Ramiro retraced his steps and managed to get into his room, with the door emitting no more than a faint squeak while his hapless victim was at her loudest. He squatted by his bed, staring at the floor, trying to understand what was happening.

How could he carve anything into the rock face, if the idea of doing it had only come to him after he’d seen the result? Even the choice of words hadn’t sounded like his own. If he’d only selected them because he’d read them, who would have made the choice? No one. Agata had told him endlessly: a loop could never contain complexity with no antecedent but itself, because the probability would be far too low. There could be no words appearing on rocks for no other reason than the fact that they’d done so.

But long before Agata had dragged the two of them to the blast site, Tarquinia had seen him falling apart. And as each new phenomenon they witnessed on Esilio made the prospect of returning with the settlers more dispiriting, she must have started searching for a way for them to stay on the mountain together – to live out their final years in a place where the dust wouldn’t see them coming, where their graves had not already been dug.

Ramiro pressed his face into his hands and fought to stay silent, afraid that if he let his tympanum stir he’d shout down the walls with some confused, alarming paean to the woman that would convince the others that he’d lost his mind. He couldn’t let any hint of the plan slip out – or even let Tarquinia know that he’d uncovered it. She hadn’t wanted a co-conspirator any more than he had, and they’d both make more believable witnesses if they’d never spoken of what had happened, never made it real in anyone else’s eyes.