Ramiro must have made a choice, Agata realised, not to seek constant updates on the state of the crops. Warned that there could be problems at the start as the plants adapted to their new conditions, he’d stepped back and left it to Azelio to monitor their health, and to offer a verdict only once it was warranted.

But Ramiro wasn’t blind, and as the flowers ceased unfurling and the stalks began to wither, Agata could see that both men were losing hope.

Bell after bell, day after day, she sketched elaborate diagrams for machines to manipulate the soil’s properties. Chemically, each mineral grain was no different from that of an equivalent on the Peerless or the home world. Physically, the distinction came down to the fact that soil on the home world had once been solid rock, while for Esilian soil, from her own point of view, that fate still lay in the future. Or in Esilio’s terms, the vast bulk of the planet’s soil had been eroded from rock . . . leaving two competing possibilities: that some small portion of it had actually been emitted from the roots of time-reversed stalks of wheat, or that those strange withered plants had failed to contribute anything before finally regaining their health and being carried away by the visitors.

Still, a plant knew nothing of the past and future of each grain of sand; the whole interaction with the roots had to make sense in the present. If she could find a way to measure the detailed distribution of thermal vibrations in the soil they’d brought with them, and then recreate that in the native soil, it would no longer be statistically reasonable for the plants to fail to absorb it.

To the naked eye, soil was just soil – and if the differences were microscopic, how hard could they be to erase? But when she took the most promising of her schemes and thought seriously about the practicalities, the measurements were close to impossible, the manipulations impractical, the computations prohibitive and the projected throughput so slow that a cubic scant of soil would have taken eons to process.

Agata deleted the sketches from her console. She peeled off her corset and lay down on her sand bed. The whole approach was a dead end: she might as well have set out to reverse the motion of every particle of air in the Surveyor in the hope of creating a breeze that would carry all the dust away.

Anything that sought to inscribe a new arrow into the soil at a microscopic level was doomed; the numbers would always be against her. What she needed was something infinitely less subtle.

Agata waited until she had a chance to speak to Tarquinia alone. ‘Do you remember telling me once that you believed Greta had put a bomb on the Surveyor?’

Tarquinia replied warily, ‘No, but I’ll take your word for it.’

‘My word that there’s a bomb?’