Under my guiding fingers Gracie slowly brings it to her mouth. She doesn’t close her lips as she sucks on the shortbread, and drool spills down her chin. I reach for a tissue from the box on the table near us and gently wipe it away.

The night Tom and I ran from my father, the night when I was nine and my mother told us to Run! and we sped barefoot over broken glass to the sanctuary of the Spar shop on the corner, I didn’t think about my four-year-old sister cowering upstairs beneath the bedclothes. I didn’t think about anything but getting as far from my father as possible before he killed me, before he killed Tom.

I didn’t think about Gracie.

It was my job to look after her, and I left her behind.

My father insisted my baby sister had fallen down the stairs. She couldn’t contradict him, because she couldn’t talk. Or walk, or brush her hair, or smile at a familiar face, or grow up and go to school or fall in love or do anything else by herself ever again.

My mother was so ashamed of herself for going back to him she told everyone Gracie was dead. She didn’t even tell me my sister was alive – no, not alive, existing, abandoned in a mental institution – until the morning of my father’s funeral seven years later. She thought it excused him: the fact that Gracie wasn’t dead after all. I don’t want you to think the worst of him, she said. Your dad’s not as black as he’s painted.

I didn’t tell Tom then, because I didn’t want him to have to share the burden of guilt I felt for leaving Gracie behind. I visited her whenever I could, and later, once I was out of medical school and could afford it, I moved her to Alexander Manor, where I was sometimes allowed to stay with her overnight.

My ‘prison breaks’.

I let Tom imagine I’m doing dark deeds in dark places when I’m visiting my sweet, broken sister because I love him just a tiny bit more than I hate myself. He’s drawn to the darkness in me: I’m not going to be the one to disillusion him.

It’s almost dark when I say goodbye to Gracie, the chill of autumn hanging in the air. I get into my car and turn the heating up, my headlights picking up a swirl of ground mist as I turn onto the gravelled drive. I should be home by eight-thirty if the traffic isn’t too heavy.

I glance in my rearview mirror as Alexander Manor recedes into the darkness behind me and almost swerve onto the grass.

‘Jesus fuck!’ I exclaim.