G.H. Ephron is the pseudonym of journalist Hallie Ephron Touger and forensic psychologist Dr. Donald Davidoff.

PW: Paranoia plays a big role in your third novel, Delusion. Your sleuth, Dr. Peter Zak, isn't sure whether the accused, Nick Babikian, is a sick man who is the victim of illness and circumstances or a terrific actor who's just butchered his pregnant wife.

HT: I really enjoyed writing Nick—researching the computer games he designs and making them "pay off" in terms of the plot of Delusion. Nick is such a complex, interesting guy.

PW: How do you choose a medical problem to inspire a book?

DD: We pull things out of my work, things Hallie is interested in. We toss out some ideas, go back and forth. In my work, I deal with people's internal belief systems as they become increasingly dysfunctional. The idea of the whole Peter Zak series is to take a different topic and play with variations around that theme.

PW: How did you and Hallie come to collaborate?

DD: We're old friends. We were sitting over dinner with our spouses, just when Hallie had decided she wanted to write. We kept drinking wine while I was talking about court cases I'd been involved with, and this light bulb went off in the middle of the table, this light bulb that only Hallie and I could see. I said, "Let's write a book!"

PW: Hallie, you grew up in a nationally known family of writers, yet you postponed writing for a long time. Why?

HT: I wanted my own spot at the table—I wanted to be different. Everybody in my family had set the bar so high. My parents were screenwriters in Hollywood (of such classic movies as Carousel and There's No Business Like Show Business). My sister Nora [Heartburn, Sleepless in Seattle] is amazingly talented. I had to get old enough to write on my own terms and not feel that I was competing with them. That's why I like doing mysteries and not romantic comedy.

PW: Don, in your work as a forensic psychiatrist, do you ever get scared talking to someone who's committed an especially grisly crime?

DD: I've been doing forensics for about 15 years. Because of my own liberal leanings, I prefer to work for public defenders, to try and give their clients a fair shake. I interview defendants in a very controlled environment, in a room with glass walls, with a guard just outside. There's a button to push to summon help, so, most of the time, I don't feel uncomfortable, but there were two instances when the authorities were concerned enough to hand me a panic button to put on my belt!

PW: You have Peter Zak live not with his mother but next door to her, which is very unmacho, something no hard-boiled detective would ever do. Why did you decide to do that?

HT: We wanted Peter to have a relative, to have some kind of family. I wanted to work against type, to make Peter a manly man who lived next to his mother. He's not a mamma's boy, and she's a tough cookie. She gets quite a role in Delusion.

PW: Peter's relationship with his cohort, detective Annie Squires, seems to be heating up. Are they finally ready to move in together?

DD: I'll just say "No comment!"

PW: Can you picture a Peter Zak TV series? It sounds like a natural.

HT: That would be great!

DD: Having a smart sleuth like Peter is appealing. When Hallie and I get into the scientific and psychological, we insist on an accuracy and realism that comes from our knowledge of the worlds of psychology and psychiatry. What makes Peter different from many sleuths is that he's never going to get into any serious fights where his life is at stake. He's going to solve these mysteries using brain power, using his knowledge of how people function, how their minds work, to inform his solutions.