In Third Strike, U.K. crime writer Zoë Sharp's Charlie Fox, an ex-British soldier turned bodyguard, faces her toughest protection assignment yet: her parents.

What inspired you to create such an atypical heroine?

Charlie came about because she was someone I wanted to read about, a strong, independent character but not “a guy in nylons.” In fiction, women with the ability to kill have a tendency to be portrayed either as psychopaths or assassins, and I had in mind that Charlie would be neither. Receiving death-threat letters through a magazine column I was writing was another prompt. It focused my mind on how people respond to danger. My first act was to sign up for self-defense lessons, which also proved to be excellent research. I put Charlie under threat, just to see how she would react.

Why did you decide to make Charlie's move to the U.S. permanent in Third Strike?

I found the process of having Charlie look at another country and another people through a stranger's eyes a very interesting one. She's always felt like an outsider looking in, and this seemed to intensify that feeling of isolation. Of course, having Charlie in the United States allowed her to carry a handgun legally, something she could no longer do if I'd kept her in the U.K. full time.

Charlie is extremely knowledgeable about weapons and defense techniques. What's your research process?

I realized that the awareness of your surroundings that you develop through self-defense training was just the kind of trait I wanted her to have. I've brought a lot of what I learned into the books, and picked up a lot more along the way. I used to be a competition target rifle shooter, so I was fairly familiar with guns before I started to write the books.

You've taken a very hands-on approach with some of your fans.

Every year, the Bouchercon mystery convention has a charity auction, where various authors put forward lots. In 2006, one of mine was a variation on the usual “have breakfast with the author.” It became “have breakfast and go to the gun range with the author”. The unusual factor was that the winning bidder has been blind since birth. She went out and bought cheap transistor radios to use for target practice. With the radios providing direction to the target, she put more holes in that outline at 10 feet than most novice shooters manage first time out. She's a brilliant example that you can do anything you set your mind to.