Caroline’s husband is killed but she can’t turn to the police without implicating herself. When one of her 10-year-old twins is kidnapped, the desperate mother is forced to resort to drastic measures to get him back. Killer Plan is the seventh book in the highly successful Geraldine Steel detective series by Pinner author Leigh Russell. The former Aldenham School English teacher talks to Rosy Moorhead about forensics, real-life crime and sipping cocktails.

What have you been up to since we last spoke, when you released the last DI Geraldine Steel novel, Fatal Act, last year?

The books have been number one on Kindle, number one on iTunes, they’re going great guns. I’ve also sold the option for them to Avalon Television, which is very exciting. I’ve also released the third book in the spin-off series about DS Ian Peterson, and I’ve also just got a deal for another crime adventure series, about a reluctant detective called Lucy Hall, which will be out next year.

What happens in Killer Plan?

It starts with a woman taking her children to the park and she has a chance encounter with somebody she went to school with and the whole story spins out from there – we have murders, a child disappearing, all sorts of things – and Geraldine is once again pitting her wits against quite a devious killer.

Where did the inspiration for this one come from?

I never get my stories from true life. I know it sounds strange but I don’t like reading about real crime, I find it too upsetting. I like my crime to be in fiction, that’s it. I don’t know where my ideas come from, I suppose they must be sparked off by something I see or hear or read. They’re all kind of a ‘what if?’ and then I just take the idea and run with it and see what happens.

Did you have to do any special research for this one into forensics or police procedures or the like?

Yes, I did. It’s very difficult to keep abreast of all the current forensics because everything is moving forward so fast. It’s phenomenal what they can do now – you can walk into a room and breathe and they can tell your hair colour and your eye colour! So even if they don’t have a match for you on their database they can rule out some people and narrow it down. That does make it trickier, writing detective novels, though!

Do these technological developments ever give you ideas for storylines?

Sometimes. In Stop Dead, the fifth book, I did play around with that – at the crime scene they find DNA evidence of somebody who was in prison and also of somebody who’d been dead for two years.

Does Geraldine’s story develop much in this latest instalment?

She discovered early on in the series that she was adopted and she’s been looking for her birth mother all this time, and there’s a big development in this book. People have been asking me about it for a long time!

What’s coming up next for you?

The next DS Ian Peterson book is out later this year, I’m flying off to the Seychelles for two weeks and then to Paris for a week to do some research for the new Lucy Hall series – somebody’s got to research watching the sun set and drinking cocktails!