I actually felt a kind of nostalgic affection for the brown house as I started to drag my suitcases from the cupboard beneath Zac’s stairs, sliding and pulling them into the wide hallway behind me.

I couldn’t help but smile at my grandmother’s blue vinyl train case, which was like seeing an old friend. When I once expressed surprise at the pretty colour, she told me my grandfather bought it for her. ‘Horribly impractical. See how it scuffs,’ she said. But she looked at it with reluctant affection. After all, she’d brought it from their farm to my parents’ house when she moved in to look after me. I in turn brought it to Zac’s, stuffed with my bathroom things and make-up.

It wouldn’t occur to Zac that I’d enter this dank and dusty place, which he avoided, given the germs that must infest it. I had to crawl inside to reach the final suitcases. They were old, made of tan canvas and trimmed with tan fake leather in the corners. The larger of the two was too bulky and heavy to comply with today’s airline specifications.

I shone my phone torch over them. Flimsy padlocks linked the zippers. I lifted each of the identification tags. Zac had written his name on both. He’d probably dragged them around the continent during his gap year grand tour, and kept them out of nostalgic fondness.

I tugged Zac’s clunky things into the hall, then unfastened my grandmother’s train case. Tucked within a silky stretch pocket on its topside was a snap-closing coin purse filled with tiny keys for old suitcase locks. The purse – quilted fabric, and brown, of course – had lived in that pocket for as long as I could remember. I could hear my grandmother’s voice. Brown is a practical colour, Holly. It doesn’t show the dirt. Hurrah for brown. For once, I was glad of my grandmother’s fixed habits. In an instant, I spilled the keys onto the stripped floorboards with a clatter.

The good thing about suitcase keys, my grandmother used to say, was that so many of them worked in multiple locks – you just needed to gauge the size by eye. Perhaps my grandmother had a bit of spy in her, too. The third key I tried fitted perfectly into the lock on Zac’s larger case. There was a satisfying click and the shackle popped out.

I wasn’t sure what I was hoping to find inside when I unzipped it, kneeling on the cold floor. Secret documents? Stacks of cash? Jane’s body? My expectations were unreasonably high, so my stomach fell when the lid of the case flopped onto the floor with a puff of dust and I saw that it was empty.