As Agata described her plan to blast their own arrow into the Esilian soil, she could see an expression of delight growing on Azelio’s face – as if she’d slipped a drawing of a flourishing garden sprouting from a bomb-shattered hillside into the stack the children had left him. There was scepticism too, but she was sure now that he would understand that it was at least worth trying.

Ramiro, though, remained as dispirited as ever. ‘If we do set off this explosive,’ he reasoned, ‘shouldn’t we be able to see some evidence of that already?’

Agata said, ‘You mean a crater?’

‘Yes.’

‘If we found a site like that, it would be useless to us. It would imply that after we set off the bomb, the crater would be gone and the sand around it would be rock again.’

Ramiro scowled. ‘Esilio doesn’t care what’s useful or useless, or it wouldn’t have killed the plants, would it?’

‘Esilio doesn’t care,’ Agata agreed, ‘but why would we go ahead and set off the bomb there, knowing that it would do us no good?’

‘Because the crater would prove that we did!’ Ramiro replied heatedly.

‘But as far as we know, there is no such crater.’ Agata met his gaze openly, trying to reassure him of her sincerity: she wasn’t playing some verbal game just to annoy him. ‘There is no crater, because if we saw it, we wouldn’t choose to make it. Esilio can’t force our hand; whatever happens has to be consistent with everything, including our motives.’

Ramiro said, ‘It can’t force our hand, but there could still be an accident.’

‘That’s true. But if we saw such a crater, we wouldn’t even go near it with the explosive.’ Agata would have liked to have taken comfort from the fact that there were no signs at the landing site of any future accident, but if the blast was capable of imposing its own arrow that meant nothing.

Ramiro’s hostility wavered. ‘I don’t know how to think about any of this,’ he admitted. He ran a hand over his face. ‘If the plants can’t bring their arrow to Esilio, why should a bomb do any better?’

‘The roots of a plant aren’t entirely passive,’ Azelio replied, ‘but they do rely on the state of the soil. I don’t think the bomb going off will rely on anything like that.’

‘But in Esilian time,’ Ramiro protested, ‘all the soil we’re supposedly going to make with this bomb has to mesh perfectly with a backwards explosion in such a way that it forms a solid rock. How likely is that?’

‘How likely are the alternatives?’ Agata countered. ‘How likely is it that the explosive will fail to detonate? How likely is it that we’ll allow it to explode in an existing crater instead – just to pander to Esilio’s arrow?’