He closed the inner door, then hesitated, gathering his courage. There was no need to use the pump – Tarquinia had already raised the cabin pressure to match the external atmosphere. He was wearing his helmet and cooling bag for protection from the dust; he switched on the coherer in his helmet, dazzling himself for a moment until he adjusted the brightness.

There was fine red dust covering the grey hardstone walls of the airlock. He hadn’t noticed it by the dimmer illumination of the safety light. He ran a gloved finger along the seal of the outer door, trying to find the point where it had been breached, but if there was a hole it wasn’t apparent.

It hardly mattered now; however the dust had entered, he was about to let in a great deal more. But as he began to turn the crank, the realisation hit him: it hadn’t come from outside. They must have brought it with them all the way from the Peerless, scattered invisibly throughout the craft, with a little more accumulating inside the airlock each time the inner door was opened. Or in Esilio’s terms: the Surveyor’s visit had just ended, and this residue was something they would soon take away with them.

Ramiro shivered, disoriented for a moment, but whether or not this account was correct there was nothing to be done about it. A small, stubborn part of him longed to leave the door closed and . . . what? Never open it at all, just to see if he could spite this unsurprising message from the future which claimed that, actually, he would? Every time they’d used the time-reversed camera, subtler but even stranger things had happened, as thermal fluctuations in the sensor conspired to create the orderly pattern of photons that the device needed to emit. Every image the camera had shown them had been encoded all along in the not-quite-random vibrations of various objects throughout the Surveyor, waiting to come together at just the right moment.

He leant against the crank and broke the door’s seal; a gust of wind forced its way through the narrow gap. Dust flew into the airlock, dust flew out, erasing all distinctions between that which they’d brought and the rest. He slid the door fully open, letting the light from his helmet carve a tunnel through the storm. Amidst the chaos, sheets of darkness fluttered, where the dust piled together in mid-air for a moment before scattering again. Cautiously, Ramiro poked his head and shoulders through the portal. He felt the warm wind insinuate itself beneath the fabric of his cooling bag, but it seemed that nothing it carried was small enough, or sharp enough, to reach his skin.