‘I can’t tell them – they’d think I killed him. There might even be my DNA on him. Forensic experts can find anything, can’t they? I didn’t do this, Sienna. Look at me! I didn’t kill Greg.’

Physically, Sienna is still, but Abby knows her mind will be in silent turmoil as she processes what she’s just learned. For so many weeks now, Abby has wondered whether Sienna had something to do with Greg’s death, but seeing her now, hearing her reaction to just the minor injury Abby inflicted upon him, she has trouble believing that. It needs to be addressed, though.

Abby needs to say something else. She can’t bear the silence. ‘There have been times when I thought… you had done it.’

Sienna’s eyes widen, but surely this can’t be news to her. Surely the police will have already looked at Sienna. Doesn’t it often start close to home?

‘I would never have hurt Greg,’ she says, her voice soft and broken. ‘That would be like hurting myself. No, worse than hurting myself. He was everything to me.’

Abby knows now that this is how strongly Sienna felt for Greg, although it’s taken all this to show it to her. Sienna never wore her heart on her sleeve. She was too strong for that, too confident. She didn’t want even Abby to see how much she needed Greg.

‘Why did you suggest the swap that night?’ she asks. ‘I know we were all drunk, but what could you possibly have wanted to gain from it? I’ve tried to work it out and I can’t understand it.’

There is no hesitation when Sienna answers. ‘I wanted to prove something to myself. I needed to know that Greg wouldn’t go for it. That he would never have wanted to spend a night with another woman and let me be with another man.’

Abby shakes her head. ‘But it wasn’t about sex, was it? So what would it have proved if he’d said no?’

‘There’s so much you don’t understand,’ Sienna says. She’s watching a young couple walk past; hand in hand, they are oblivious to their surroundings, wrapped up only in each other. ‘I bet they’ve only just met,’ she says. ‘There’s no way they’ve been together long.’

Abby watches them too. ‘Or maybe they’re just with the right person.’

‘Greg hardly touched me the last few months,’ Sienna says.

Her declaration catches Abby off guard. ‘Well, lots of couples go through a tricky phase. Maybe he was stressed at work.’

‘No, it wasn’t that. He was pulling away from me. Shutting me out. It’s almost as if he didn’t want to be around me.’ She shakes her head. ‘Maybe part of me wanted him to sleep with you.’

‘What? But why? I would never have done that.’