I told Lizzie to start from the beginning. I realize now that may have been a mistake. I’m just surprised she didn’t start by recounting her birth. Blimey, this girl likes the sound of her own voice.

“I’m really in debt,” Lizzie says, winding a tissue through her fingers. “I keep thinking that if I have the latest bag or whatever, they’ll let me be friends with them. And it does sort of work. I mean, they ask me to parties sometimes, and if I’m in the same club they’ll let me sit with them if I buy lots of drinks. But Dad’s actually quite strict about my credit card, he monitors it online and he shouts at me if I go over a grand, which is nothing, actually, I can’t believe he’s that fussy when he’s a multimillionaire, you know?”

Lizzie’s incapable of holding more than one thought in her head at any one time: from her indignant tone, I can tell that she’s so resentful at her father’s injustice that she’s temporarily forgotten to be frightened of me and Taylor. She starts shredding the tissue she’s holding, ripping it up angrily. Bits of white floaty paper drift off in the breeze and fall to the grass below the bench.

“Anyway, I’m really skint after buying this bag.” She looks dolefully at the ghastly chartreuse thing with its dripping straps and buckles and shiny dangling bits. “I wanted to go out this weekend, but I can’t, because I haven’t got a penny, and then she offered me all this money if I’d just leave a note for you, Scarlett.” Lizzie looks up at me, her eyes still swollen, but with a genuinely imploring expression that makes me think she’s telling the truth here. “She swore it wasn’t anything bad, just that she didn’t want you to know it came from her.”

“Why not?” Taylor asks.

“I don’t know, she didn’t tell me and I didn’t ask. I mean, it was two hundred and fifty pounds! Just for leaving you a note! And then the first one you had a pen leak on, so I had to go and get another one from her, which was really hard to organize because I had to be back by curfew and she made this huge fuss about coming out on the tube to meet me. Wait.  .  .  .”

The penny dropped. Lizzie stares at both of us in shock.

“You didn’t have an ink leak, did you?” Lizzie says, her voice rising. “It was all a setup. You did that deliberately so I’d have to get another note and you could watch me put it in the desk and I still don’t know how you saw me! Unless Meena saw me, but when I came out of the room she was halfway down the corridor. Did you have a video or something in there?”

Taylor and I just look back at her, stone-faced, not giving anything away.

She sighs. It’d be a sob if she had any tears left. As it is, she just looks down at the shredded tissue on the grass, and sighs again.

“No one ever tells me anything,” Lizzie complains. “That note was sealed up, so I couldn’t see what it was, and now you won’t tell me how you knew it was me! It’s so unfair.”

“Life sucks, Lizzie,” Taylor says nastily. “Deal with it.”

I expect now I should be good cop to Taylor’s bad, but I haven’t got the energy to pretend to be nice. This last half hour has been really draining. I decide that we’ll go for bad cop/bad cop instead. It’ll be quicker.

I fix Lizzie with a hard stare, and say:

“What’s her name, Lizzie? The girl who paid you to slip me that note?”

Lizzie starts shredding another tissue.

“I promised I wouldn’t tell,” she whines. “And she was going to let me go clubbing with them on Saturday and not make me pay for everything, like they usually do  .  .  .”

Taylor walks over to the bench, kneels down in front of Lizzie, and grabs her shoulders. Blimey. Taylor must look enormous from that angle, her jaw jutting forward, her arms swelling under her T-shirt. Her hands are really strong, too, and calloused from all the rope climbing. Lizzie visibly wilts in her grasp.

“You’re out of time,” Taylor says. “Give us the name. Now.”

Double-blimey. Taylor is fantastic at being bad cop. I just hope she never turns on me.

Lizzie droops as if she has no backbone at all, as if she’s just made of jelly. Her head hanging, she stares down at the grass, and whispers a name, so softly that I don’t catch it.

“What did she say?” I demand.

My heart’s pounding. We’re getting closer to finding out at least part of this mystery, the real truth of what happened that night, the answer to why Dan died.

Taylor lets go of Lizzie, who flops onto the bench.

“Nadia,” Taylor tells me. “She said Nadia.”