She changed into her pyjamas and climbed into bed. I heard the rustle of her sheet and blanket as she pulled them up over her shoulder and turned away from me.

What was wrong with her? After a few minutes of silence, I rolled in the opposite direction – towards the window – so that our backs were facing each other. Eventually I gave in to sleep, allowing the dark dreams to flood back into my exhausted brain.

The day after that, Mags was out of the house at dawn and didn’t come home until after supper time, and the same thing happened the next day too. I spent both days up in the lantern room, polishing the lamp, and recording the weather conditions and shipping movements in Pa’s logbook. I stared out to sea, hypnotized by the slow-twisting shape of the Wyrm beneath the waves, trying to work out what had happened to my sister. Something had shifted again – she was just as she’d been before Dunkirk, back in the early spring, when I’d felt I hardly knew her at all. I needed to talk to her about being evacuated – had she managed to speak to someone about it? Had she sorted it out somehow? We hadn’t heard anything from Mrs Baron for a couple of days now.

Perhaps that cold, lonely silence between us would have gone on for ever, if it hadn’t been for what happened to Mrs Rossi and her husband.

The police came for them and took them away.

They weren’t spies – they hadn’t done anything wrong at all – but their home country, Italy, had now joined the war – on Hitler’s side, not ours. With everyone in the country so angry and frightened and expecting an invasion at any minute, Mr Churchill had ordered the police to ‘Collar the lot!’ – anyone who could potentially be a supporter of the enemy; anyone born in the wrong country. It didn’t matter now if you were a Category B or C enemy alien – you were likely to be rounded up for the internment camps, and some people were being deported too.