The poison garden left unlocked and unguarded by Jack Grant.

It had already killed one little girl.

Dear God, I prayed, as I began to sprint towards the back of the house, towards the path down through the shrubbery, my feet slipping in the too-big Wellingtons. Please let it not claim another.

But as I rounded the corner of the house, I found her.

She was lying crumpled facedown below my bedroom window, sprawled across the cobblestones in her nightdress, the white cotton soaked through and through with blood, so much blood I would never have imagined her small body could hold it all.

It ran across the cobbles like treacle, thick and sticky, slicking my knees as I knelt in it, clinging to my fingers as I picked her up, cradling her, feeling the birdlike fragility of her little bones, begging her, pleading with her to be okay.

But of course it was impossible.

She would never be okay again. Nothing would.

She was quite, quite dead.

The next few hours are the ones that the police have made me go over again and again, like nails scratching and scratching at a wound, making it bleed afresh every time. And yet, even after all their questions, the memories only come in snatches, like a night illuminated by flashes of lightning, with darkness in between.

I remember screaming, holding Maddie’s body for what felt like the longest time, until first Jack came, and then Rhiannon, holding a wailing Petra in her arms, almost dropping her when she saw the horror of what had happened.

I remember her wail, that awful sound, as she saw her sister’s body. I don’t think I will ever forget that.

I remember Jack taking Rhiannon inside and then trying to pull me away, saying she’s dead, she’s dead, we can’t disturb the body, Rowan, we have to leave her for the police, and I couldn’t let her go, I could only weep and cry.

I remember the flashing blue lights of the police at the gate, and Rhiannon’s face, white and stricken as she tried to comprehend.

And I remember sitting there, covered in blood on the velvet sofa, as they asked me what happened, what happened, what happened.

And I still don’t know.

*

I still don’t know, Mr. Wrexham, and that’s the truth.

I know what the police think, from the questions they asked, and the scenarios they put to me.

They think that Maddie went up to my room to find me missing, and that she saw something incriminating up there—perhaps she went to the window and saw me creeping back from Jack’s flat. Or perhaps they think she found something in my belongings, something to do with my real name, my true identity.

I don’t know. I had so much to hide, after all.

And they think that I came back to find her there, and realized what she had seen, and that I opened the window and that—

I can’t say it. It’s hard even to write it. But I have to.

They think that I threw her out. They think that I stood there, with the curtains blowing wide, and watched her bleed to death on the cobblestones, and then went back downstairs to drink tea, and wait calmly for Rhiannon to come home.

They think that I left the window open deliberately, to try to make it seem like she could have fallen. But they are sure that she didn’t. I am not certain why—I think it’s something to do with the position of where she landed—too far away from the building to be a slip, with an arc that could only have been caused by a push, or a jump.

Would Maddie have jumped? That’s a question I have asked myself a thousand, maybe a million times.

And the truth is, I just don’t know.

We may never know. Because the irony is, Mr. Wrexham, in a house filled with a dozen cameras, there are none that show what happened to Maddie that night. The camera in her room shows nothing but darkness. It points away from the door, at the girls’ beds, so there is not even a silhouette in the doorway to show what time Maddie left.

And as for my room . . . oh God . . . as for my room, that is one of the bricks in the edifice of evidence the police built against me.

“Why did you cover the security camera in your room if you had nothing to hide?” they kept asking me again, and again, and again.

And I tried to tell them—to explain what it’s like to be a young woman, alone, in a strange house, with strangers watching you. I tried to tell them how I was okay with a camera in the kitchen, the den, the living room, the corridors, even with cameras in the girls’ rooms. But that I needed somewhere, just one place, where I could be myself, unwatched, unmonitored. Where I could be not Rowan but Rachel—just for a few hours.

“Would you want a camera in your bedroom?” I asked the detective, point-blank, but he just shrugged as if to say, It’s not me on trial, love.

But the truth is, I did cover up that camera. And if I hadn’t, we might know what happened to Maddie.

Because, I didn’t kill her, Mr. Wrexham. I know I’ve said that already. I told you in the very first letter I sent you. I didn’t kill her, and you have to believe me, because it’s the truth. But I don’t know, writing these words in my cramped cell, with the Scottish rain drizzling down the window outside . . . Have I convinced you? How I wish I could persuade you to come here. I’ve put you on my list of visitors. You could come tomorrow, even. And I could look into your eyes and tell you—I didn’t kill her.

But I didn’t convince the police of that. I didn’t convince Mr. Gates either.