.

      ‘Perhaps next time, Angus, we can move to Vladivostok?’

      Angus chuckles politely. He already looks more Scottish, here in Scotland. His cheeks are ruddier, his stubble is darker, he is definitely a bit dirtier: more rugged, salt-bitten and masculine. Instead of his architect’s purple silk ties he has scratches on his hands and paint flecks in his hair. He’s been here three days ‘preparing the place’ so as to make it habitable for me and Kirstie.

      ‘Josh is going to give us a lift, in his boat.’

      ‘You guys,’ Josh says, kissing me warmly, on both sides of my face, ‘you guys REALLY HAVE to get a boat. Torran is a nightmare without a boat, the tides will drive you doolally.’

      I force a smile. ‘Thanks, Josh, that’s just what we need to hear, on our very first day.’

      He grins in that boyish way. And I remember that I like Josh. He is my favourite of Angus’s friends: it helps that he is a non-drinker – completely sober. Because he slows down Angus’s boozing.

      Like a team of explorers abseiling, we climb down the steps of the pier, to Josh’s boat. Beany goes second, chivvied by Angus, then leaping with unexpected grace into the vessel. Kirstie follows: she is excited, in that eerie calm way that Lydia used to get excited; her head is perfectly still, staring out, as if she is catatonic, but you can see the shine in her eyes. Enraptured.

      ‘All aboard, shiver my timbers, Torran ahoy!’ says Josh, for Kirstie’s benefit – and Kirstie giggles. Josh poles the boat into the deeps and Angus gathers in the rope, very quickly, and we begin our miniature yet crucial voyage, rippling around the bigger tidal island, Salmadair, that divides Torran from Ornsay.

      ‘That’s where the packaging billionaire lives.’

      Half my attention is given to Salmadair – but the other half is fixed on Kirstie’s happy little face: her soft blue eyes gazing in wonder at the water and the islands and the enormous Hebridean skies.

      I remember her shout of despair.

       Mummy Mummy come quickly, Lydie-lo has fallen.

      Again, it strikes me, with painful force, how those words are, really, the only evidence we have for believing it was Lydia that died, not Kirstie. But why did I believe those words?

      Because there was no obvious reason for her to lie. At that moment of all moments. But maybe she was confused in some bizarre way. And I can see why she might have been confused, given that the twins were always swapping names, swapping their whole identities, during that fateful summer. When they were dressed alike, when they had the same haircut. It was a game they liked to play, that summer, on me and Angus. Which one am I, Mummy? Which one am I?

      So maybe they were playing that game that evening? And then disaster happened. And the fatal blurring of their identities froze over, and became fixed, like a flaw in ice.

      Or maybe Kirstie is still playing this game. But playing it in the most terrifying way. Perhaps that is why she is smiling. Perhaps she is playing the game to hurt me, and to punish me.

      But punish me for what?

      ‘OK,’ says Angus, ‘this is Torran Island.’