Tefwe and the drone were at the foot of the outcrop, just a vertical metre and a few shattered-looking boulders away from the surface of the desert. Tefwe was standing and Hassipura was hovering level with the woman’s head, performing some maintenance on a fragile-looking raising screw. The raising screw was powered by the fierce sunlight falling on a small semi-circular array of solar panels part-encasing its lower quarter.

“I see,” the woman said. “Do you choose what to forget, or do you just let things disappear randomly?”

“Scoaliera,” the drone said, “if I chose what to forget, I would very likely have forgotten all about you.”

The screw, one of a dozen or so at this lowest level of the rocks, was a couple of metres tall, and thin enough for Tefwe’s fingers to have met, had she grasped it one-handed. The foot of the device lay in a pool of sand about a metre across; the slowly rotating screw twisted lazily in the dark-gold grains, raising them inside a transparent collar with a hypnotic steadiness to deposit the lifted material, a minute or so later, into another pool on a higher tier of the outcrop, where a second level of raising screws and sand-wheels like pieces of giant clockwork would transport the material further up, and so on, for level after level and diminishing tier after diminishing tier until a single last raising screw, buried in a tunnel inside the dusty peak of the tor, deposited a small trickle of sand to an overflowing pool at its very summit.

“That is ungallant, and, I suspect, also not true.”

“Let us test that, shall we, should you ever come to visit me again?”

“I don’t believe you delete memories at random.”

“They are chosen at random and buffer-binned; whether they are finally deleted is a matter of choice.”

“Ah. Might have thought so.”

The drone had subtly sculpted the outcrop over the decades and centuries it had lived here, cutting channels, pools, cisterns, tunnels and reservoirs into the rock, building structures that at least resembled aqueducts and creating, had the whole complex been filled with water, what would have been a kind of secret water garden, albeit with rather steeply inclined canals and aqueducts.

But the outcrop held no water at all. Instead it was sand that moved within the tunnels and channels, sand which was lifted within the raising wheels and screws, and sand which fell in little whispering falls and moved liquidly down dry weirs.

“Whatever makes you think I’d wish to visit you again after being so roundly insulted?”

“That fact that I have insulted you just as roundly in the past to so little effect,” the drone said smoothly, “for here you are. Again.”