I woke in the middle of the night with a crazy idea. I got up and started writing it down immediately. My heart was pounding in my chest as I rehearsed my speech in front of the mirror. It could work, and it could give us the inside track we’ve been desperately craving. My hands are still trembling.

I have spent the day trying to get the DI alone so I can speak to her, but the top brass have kept her away from the incident room all day. As crazy an idea as it is, I’m sure she’ll go for it. Matthews is not afraid to challenge convention.

But it gets to 7.00 p.m., and she calls the team together for an evening brief. She admits that the DSI is considering replacing her on the enquiry, to bring fresh eyes in. The DSI has never been convinced that the murders were linked, and our lack of progress gives him all the rope he needs to hang her out to dry. But I am certain she is right. I have studied the post-mortem reports, and the images of the scarring left by the killer’s blade. I’ve even taken copies of the images home to study more.

She is about to end the brief when I tentatively raise my hand again. ‘What about an undercover op, ma’am?’ I say weakly.

She looks confused, so I try and explain how it could work. The speech I spent all night rehearsing has disappeared from my memory, and I struggle to get my words out. There are murmurs of derision from some of the team. They think I’m just out to make a name for myself, but it isn’t that. I made a promise to Steph, and I’m determined to fulfil it.

The DI thanks me for my suggestion, but dismisses it out of hand. She releases the group, and I see her walk into her office and close the door. She sits behind the desk and buries her head in her hands.

I saw the newspaper article this morning. One of the tabloids ran a fourth-page story about her marital problems and how she isn’t fit to head this investigation. It was vicious, and I can’t help but pity her. I’m relieved that nobody has dug up my secrets. Imagine if your worst – most shameful – secret was laid bare for all to devour and judge. How would you feel?

I find myself knocking on the door. When I begin to speak about going undercover, she raises her hand to silence me, but she doesn’t realise I won’t take no for an answer. I tell her that it’s our last shake of the dice. I tell her we can upload my profiles to different sites and I add that I’ll do it with or without the Met’s support.

She says the DSI won’t sign off on the budget needed to surveil potential suspects. I tell her we don’t need a big team. Just enough cover for one officer to watch the hidden camera I’ll wear, and another in support.

The DI warns me that I’d be putting my life on the line, and that my dad wouldn’t have approved. I remind her that he lost his life in the line of duty, and would want me to risk everything for the career he dedicated his life to for more than twenty years.

I can see she is waning.

Deep down, I’ve already decided that I’m going to act on this idea whether she gives it the green light or not. I’m sure it was Pop who sent me the idea. He’d want me to do it.

‘There’s no way to guarantee he’d bite,’ she argues.

‘We’ve nothing to lose, ma’am. With respect, it beats sitting on our arses hoping he drops into our laps.’ I blush at my outburst, but she smiles.

‘I admire your passion, Amy. We’d have to create an unshakeable cover story for you, and set you up in temporary accommodation.’

‘I’m willing to do whatever it takes, ma’am.’

‘If we were to do this, we’d need to keep it quiet. God knows there have been enough leaks from this office already. The fewer who know what we’re doing, the better.’

I can feel my lips curling into a smile. ‘I understand, ma’am.’

‘Tell me one thing first: why do you want this so badly?’

I’m not sure how to answer her question, as I’m concerned the wrong answer will dissuade her from pursuing it. I could tell her it’s because I made a promise to Steph, or I could tell her it’s to honour my father’s memory, or even that it’s my duty as a Met police officer. But none of those answers feel right. They’re all true, but what drove me to step into her office and petition her, was more than that.

‘Would you hate me if I said I felt it was my destiny, ma’am? Every decision I’ve made to this point has led me here. I feel deep down that I need to do this if we’re ever to stand a chance of catching him.’

She is silent as she watches me, and I can almost hear the cogs turning in her mind. Her face is neutral. Oh God, does that mean she hated the answer? Although a ‘No,’ won’t stop me, I know it will work better with her support.

Matthews finally breaks the suspense with a smile of her own. ‘Okay, Amy, I’ll run it up the line to the DSI. I’m sure he’ll reject the suggestion, but I have a trick or two up my sleeve.’ She winks, before dismissing me.

I feel like a massive weight has been lifted from my shoulders as I close her door behind me.