Ramiro hadn’t thought about the technical aspects of the system for years, and as he reacquainted himself he was surprised by its apparent fragility. ‘Disrupt the light for a flicker, and the flow of information is cut. There’s no need to damage anything.’ Although the messages were constantly being converted into a less transient form to be boosted and re-sent, that version of the data only endured forwards in time – it couldn’t bridge a gap into the past. He’d often pictured the messages as a storehouse of documents, a kind of future-archeological find, but they were much more vulnerable than anything written on paper, or even in the energy states of a memory chip.

‘Could we launch some small objects into the external light paths?’ Tarquinia wondered. ‘If each one starts on the mountain close to one of the channel’s outlets, it could probably occult the target star without being picked up by a surveillance camera first.’

Azelio said, ‘The outlets will have to be on the base of the mountain, won’t they?’

‘Yes,’ Tarquinia replied. ‘Unless they’ve turned everything around while we were gone.’

‘We’d need to know exactly which orthogonal stars they’re using,’ Agata pointed out.

‘Maybe our collaborators will have that information already,’ Ramiro suggested. ‘So if we can offer them some miniature automated craft to fly up from the mountain and block those stars, why wouldn’t they use them?’

Azelio said, ‘So who’s going to build these things without being noticed? They’ll need accelerometers and photonics in order to navigate with any precision. If we make them ourselves on the Surveyor, we won’t stand a chance of smuggling them out when we dock. But on the Peerless, all the workshops and stores will be under surveillance.’

‘We could release them before we dock,’ Agata suggested. ‘Send them out to hide somewhere. If they’re small enough, and we time the whole thing carefully, they could pass from the Surveyor to the slopes undetected.’

‘And then what?’ Azelio pressed her. ‘They adhere to the slopes somehow, and then crawl towards the base – like insects crawling along a ceiling?’

‘Yes.’ Agata wasn’t backing down, but the proposal was growing more ambitious by the moment.

‘And then later,’ Azelio said, ‘since we won’t know the coordinates in advance, we have to be able to instruct them, remotely, to crawl to a particular take-off point and then fly along a certain trajectory. Without the signal being detected.’

Tarquinia disagreed with his last claim. ‘If a brief encrypted signal is picked up by the authorities, what can they do about it? So long as they can’t pin down the exact source or destination, mere detection need not be a problem. Even if they take it as a sign that some form of attempted sabotage is under way . . . they would have had that possibility in mind for the last three years, regardless.’