Gaia nods, and instantly her tummy flutters. She told a lie. She tries to tell herself that actually she didn’t tell a lie because she didn’t speak, but even so she feels bad. But it feels wrong to say that no, she doesn’t like her baby sister. That seems mean, even though it’s the truth.

‘I hated my sister,’ Derry says then, and Gaia lifts her eyes to her, shocked. ‘She was mean to me. She’d pinch herself and tell Mum that I did it until I put tacks in her shoes. She didn’t pinch herself again after that.’

Gaia’s mouth falls open. She has no idea what to say, though it’s an odd kind of relief to know that she isn’t the only person in the world who dislikes her own sister.

In the basement Aurelia flicks off the garish overhead lights and turns on the red safelight that, mercifully, is still working. She gets to work quickly, worried that Derry might fall asleep with the baby on her lap.

She slides the negative strip under the small square eye of the enlarger and opens the aperture on to the sheet of A4 developer paper. Then she uses the tweezers to dip the paper into the first tub of liquid, then the second. In college she would use her fingers on account of a lack of funds to buy tweezers – she got used to burning her fingertips off in the acid – and she often did this same process in the pitch dark, and without a timer. Even now, she counts the seconds in her head. One, two, three, four … She holds her breath. This is a holy moment, the closest she has come to prayer and worship – bringing the past to life on a blank page. Coaxing it there, and fixing it so that it doesn’t become over- or under-exposed, both of which would inform the eye that it’s a poor simulacrum and not the true past. Get the image right and the photograph hooks you back to the moment it captures with all its sensory context – smells, sounds, even the mood of the day.

But when she glances down at the finished image, she’s confused. The image is obscured by a word drawn in capitals, as though on a windowpane, or perhaps in the wet sheen of the film: MUST.

She can’t make any sense of what she’s seeing, or why she should be seeing it. Her thoughts race to work out how the image could have absorbed these letters. Sometimes an over-exposure will cause cloud-like shadows and shapes to appear, but this is a word scrawled over the image of Gaia spinning in the snow, her head tilted to the sky.