Later, people asked me whether I knew others who’d been at Harbour. Did you see my brother, did you see my wife? Yes, I said. I saw others at Harbour. I was forbidden from speaking to them. I saw them shuffling down the passageways, barefoot in their linen shifts, their mouths drawn thin, their eyes huge. And I heard them, day and night. I heard the wailing and the sobbing coming from their rooms.

They all looked so much older than us. So much worse. At the beginning I pitied them.

Dr Bellavit wanted to know what it was I was holding onto, emotionally.

We talked about my father and mother, little more than blurred shapes to me by then – a bark of laughter, a bracelet slipping down a wrist, the rustle and crack as the morning’s newspaper was shaken out. We talked about Aunt Caroline: her blue eyeliner and hair gel, the word she taught me when I was seventeen: malingerer.

‘You are what, Thomasina, twenty-eight years of age?’

‘Twenty-nine.’

‘And you have never known other types of torment? Those that might be inflicted by a boyfriend, say? A paramour?’

She smiled encouragingly.

‘No,’ I said, though even as I said it I saw Gordon’s face, his narrow hips swaying as he danced in our living room, his fork ensuring the peas and corn were separate on his plate.

‘Thomasina,’ Dr Bellavit said, ‘I understand your reluctance. I know that you are close with your half-sister.’

I sat up at this. It was true that Tilly and I were half-sisters. She had her mother’s fair skin and honey-flecked eyes, the kind of hair that turns blonde in the sun. I looked nothing like her. My father always said: you are as dark as a pirate. And it was my mother’s illness I had inherited, though she never had a diagnosis for it. She never sought treatment. She would only say she was delicate, and vanish discreetly to the powder room for hours on end. I never asked about the source of Tilly’s illness. We never spoke of our different mothers. It was the one thing that, even in our worst arguments, stayed unsaid, hovering in the air.

But I hadn’t mentioned this to Dr Bellavit. Tilly must have told her.

Dr Bellavit gave me a stern look. ‘You must understand that you are here as an individual. Not as half of a pair. This is your time.’

She reached across the desk, took my hand. ‘And your path to wellness will be unique. Do you see?’

She was smiling at me again. I didn’t want to fail her test. My guts slithered in a spasm of pain. I nodded.

‘Good girl,’ she said, and clicked her pen.

In the evenings, we were allowed to walk to the beach. This is where Tilly and I found one another and broke the no-talking rule.