I hated this first bit. Tree roots cobwebbed the walls of the tunnel and dangled down into our path. Sometimes they were sturdy enough to be helpful – you could grip them and lower yourself around the steep, twisting corners; sometimes the thicker roots blocked the way, hanging there like pale stalactites, and you had to hold your breath as you squeezed between them. They were rough and scaly, and caught on my woolly hat and hair. The passage was so low that, in places, we had to wriggle on our backs or bellies. My left foot caught in a root and, for a second, I couldn’t budge. As Michael and Mags got further ahead, the light of the torch died out completely, plunging me into darkness.

‘Mags!’ I called. ‘I’m stuck.’

‘Just wriggle your way through, Pet – pretend you’re a mole or something.’

I forced my foot back, hearing the root tear behind me. Some loose soil pattered down from the ceiling of the tunnel. I forced in a deep breath of the damp, earthy air and struggled on, following my sister’s squirming feet. I felt myself getting angry with her, exactly as I had in the rowing boat on the day of the crabbing competition. Why did I let her get me into scrapes like this?

As we got deeper inside the cliff, the tunnel became steeper. The walls here were chalky – pale and smooth as old bones. There were parts that were almost high enough to stand up in, with steps carved into the chalk, and lower stretches where we had to tuck down on our haunches and skid and slither our way down into the darkness. I felt my boot scrape against something sharp and the same thing tore at my coat. I thought about how angry Mutti would be when we got home and she saw the state of my clothes – and then I remembered that Mutti wasn’t at home any more. Tears started burning in my eyes and I had to bite my lip. Then, dim morning light illuminated the tunnel ahead, and the passageway twisted around a tight corner, suddenly opening up into a much larger space.

Here, halfway down the cliff face, was a round cavern with two window-like openings that looked out over the sea. This was Dragon Bay Cave. It must have been a perfect lookout spot for the smugglers who had first used the tunnel all those years ago, as they could have watched the boats making their way around the dangerous coastline, flashing signals to them with lanterns held up at the round, chalky windows.

Michael stood at the right-hand window now. ‘Such a fantastic view,’ he was saying. Then, more quietly: ‘I love being here with you, Magda.’

I was confused. Had they been here together before, then?