As Agata trudged up the rocky incline, the patch of bright ground beside the Surveyor remained visible in her rear gaze. But it looked so out of place against the dark valley floor that a part of her mind began to discount it, treating it as nothing but a flaw in her vision. The first few times she felt it vanish from her mental map of her surroundings she panicked, scanning the view for the comforting beacon until it snapped back into focus, acknowledged again as real. But after a while she stopped worrying and let it fade into the landscape. Tarquinia and Ramiro were not going to turn out the lights and hide from her. When the time came she’d have no trouble finding her way back.

Ahead, above the grey hills, the sky could not have marked the way more clearly. The direction along Esilio’s axis that they’d chosen to call ‘south’ pierced the bowl of stars about a twelfth of a revolution below its bright rim, and from this valley in the southern mid-latitudes that celestial pole remained perpetually in view, with the rim twirling around it like a burning hoop and the stars in between never setting.

Azelio walked beside her, carrying two of his potted seedlings from the final dozen he’d held in reserve. He wasn’t complaining, but she could see him struggling with the weight as the slope increased.

‘I’d be happy to take one,’ she offered.

‘Thanks, but I’d rather you had nothing to distract you from your own load,’ he replied.

Agata raised the bomb effortlessly above her head. ‘It hardly weighs anything. And even if I drop it, it’s not going to go off.’ Tarquinia had assured her that the explosive could only be triggered by a bright pulse of light at a specific wavelength, and the only means of delivering that pulse was strapped securely to her tool belt.

Azelio said, ‘I’m more worried that you might damage the detonator and we won’t be able to set it off at all.’

‘Fair enough.’

Azelio had identified a promising outcrop in the images they’d taken from orbit – a body of rock whose spectral signature suggested that it could give rise to fertile soil. No one had objected when Agata had volunteered to accompany him to the site, but she still felt slightly guilty at having wormed her way out of the tedious business of moving everything back into the Surveyor. Blowing up a hillside would be vastly more enjoyable than reassembling cooling pipes and restocking the pantry.

‘Can we rest for a bit?’ Azelio suggested.

‘Of course.’ Agata placed the bomb gently on the ground, then sat beside it, positioning her body so she’d be blocking its way if it began to slide. Azelio did the same with his plants.

‘Do you think they already know how this ends, back on the Peerless?’ he asked her.