The Vow: the gripping new thriller from a bestselling author - guaranteed to keep you up all night!

Kimberley fall out of love with her boyfriend. It was supposed to be completely harmless, more of a joke rather than anything serious. But at the last minute, Emily added something extra when my back was turned. It had hemlock in it, I think. Possibly digitalis, too. It killed Kimberley. Bill, it was the most terrible time.’ I break off, as a look of shock crosses Bill’s face. Shaking my head, remembering the events that day, I go on. ‘The police have been talking to Emily about it – or Amy as she is now. She’s told them this cock and bull story about how it was me who added the poison. I’m really worried they believe her.’ Pausing for a moment, I stare at Bill – it’s imperative he believes me. ‘She’s already in a lot of trouble. She was recently charged with the murder of a man.’ I hesitate again, knowing how implausible this is going to sound. ‘The man’s name is Matthew Roche. She was living with him. They were about to get married.’ I look at Bill. ‘The thing is … You couldn’t make this up, Bill. A few months ago, I met Matt in a bar. He told me his relationship with Amy was over and we started seeing each other. The night he disappeared, he was about to tell her he was leaving her – for me.’

Bill listens without saying a word, a look on his face I can’t read. None of this is what I wanted. I never set out to reveal what Amy did all those years ago. But I’m left with no choice but to defend my position. Amy is guilty, weak, selfish. The police should be able to see that now. But for all their razor-sharp insight and knowledge of the criminal profile, they’ve clearly missed something. I go on. ‘I know. What are the chances. Even to me, it sounds implausible. But the problem is, what if they believe her?’ My voice drops to a whisper as I clutch his arm. ‘I didn’t do it, Bill. Even though I’ve no way of proving it. You have to believe me.’

‘Of course I do.’ His face is grim. ‘We’ll see what they have to say. If you’re sure there’s nothing else I should know, let’s get this started.’

I shake my head. ‘Thanks for coming.’ I’m genuinely grateful, my words heartfelt but I’m nervous. Not only is he my best hope, he’s my only hope. If Bill can’t help me, then no-one can.

*

In all the years as a solicitor, for the first time I’m on the other side, with someone else acting on my behalf. When PC Page and DI Lacey return, Bill is straight onto it.

‘I’d like to know exactly why you’re holding my client.’ Bill speaks with an authority that comes from years of experience, that so many solicitors lack.

‘Then let us tell you.’ The DI is unruffled. ‘In 1996, a teenage girl tragically died. At first, her death was thought to be an accident. But a post-mortem revealed she’d ingested enough digitalis and hemlock to cause respiratory and cardiac arrest. Her grandmother was a herbalist and had a collection of dried herbs and extracts, which she kept in labelled jars. There was, however, one jar that was kept separately. A jar that someone found and that day, deliberately added to her drink, so that she ingested enough poison to kill her.’

‘What does this have to do with my client?’ Bill’s voice is calm.

‘The teenager’s name was Kimberley Preston. She had a sister, Emily, who was close friends with Ms Rose. In fact, it’s fair to say you were very close, weren’t you, Ms Rose?’

‘You don’t have to answer that.’ Bill interrupts. ‘Go on.’

‘Ms Rose had a crush on Kimberley’s boyfriend, Charlie. Between them, Ms Rose and Emily Preston cooked up a herbal concoction to make Kimberley fall out of love with Charlie. It was concocted from fairly benign substances – but at the last minute, somebody added something else, primarily the digitalis and hemlock that killed Kimberley. According to our witness, that was you, Ms Rose.’

It’s what I’d known Amy would tell them. By getting in first, she’s ahead of me, her story already lodged in their minds. Bill’s quiet for a moment. ‘And apart from this so-called witness, what proof do you have of this?’

The DI sits back. ‘I’d like to hear Ms Rose’s version of events. Ms Rose?’

The moment of truth, when I explain why she’s told them this. ‘It’s true. We made up this herbal potion. We got a bit carried away. But I never expected Amy to add the poison.’

The DI interrupts. ‘She told us about the small bottle labelled darkness.’

Silence fills the room, as I nod, my stomach turning over. ‘Amy was jealous of her sister. She was obsessed with her boyfriend. She wanted Kimberley to dump him, but at the last minute, I think she saw her chance and got carried away.’

DI Lacey shakes his head. ‘And the pair of you told no-one.’

Ashamed, I nod. ‘But in actual fact, Kimberley was hit by a car.’

‘Which would never have happened if the poison wasn’t taking effect,’ the DI points out. ‘In any case, the post-mortem showed she’d ingested enough of it to kill her.’

‘I don’t remember the details.’ My voice is low.

‘Tell us the reason you and Emily kept your secret all this time, Ms Rose.’ The DI’s voice is harsh.

I shake my head. ‘I think we both wanted to forget. Nothing we did was ever going to bring Kimberley back. My parents moved me to another school. After that, we lost touch.’

‘Let’s go back a bit.’ The DI pauses. ‘To right after Kimberley was hit by the car. What did you and Emily do next?’

‘I don’t know. We were too shocked to do anything. It was horrific.’ My shoulders tense as I remember.

‘Not too shocked to steal away and cut your fingers, then press them together in some sort of twisted little ritual