LAPD detective Tully Jarsdel tackles a serial killer in Schneider’s What Waits for You (Poisoned Pen, Jan.).

Why did you make Tully a former PhD candidate in classical antiquity?

I was in a tough position, because I wanted to write police procedurals without a background in law or journalism or policing. I knew there was no way I’d be able to pull off a grizzled veteran detective as my main character. It would ring totally false. Since I’m an outsider to that world, I made my protagonist an outsider as well. I tried to turn a weakness into a strength. Also, with him being a polyglot and historian, he has a tremendous amount of esoteric knowledge he can draw on.

Do you have a character arc for Tully?

It’s tricky. The character has to grow and change and mature, but without losing the traits the readers enjoyed about him from the beginning. The model for how to do this successfully is Buffy from Buffy the Vampire Slayer. She gets stronger and wiser throughout, but never loses her spark, her fierce intelligence, and her observational sense of humor. I don’t have a specific arc in mind, since each book is going to ask something new of him, but I’ll always try to stay true to his core personality.

Where did the Creeper, a murderer who hides in his victims’ homes before striking, come from?

Nightmares, mostly. Waking nightmares—the sort that nibble at the corners of an otherwise sunny day. My aim was to create less a character than a kind of living composite of our biggest anxieties—those being the fears of suffering and of the unknown.

How did being a magician help you as a mystery writer?

It’s helped in the sense that a mystery is essentially structured the same way as a good illusion. In visual magic, for example, you have several basic plots—transpositions, transformations, vanishes, and appearances. Everything you see in a show is going to be a variation on one of those standard story lines. Same thing with mysteries. In mysteries, killers are the magicians. They ask themselves, “How can I give the illusion, as convincingly as possible, that this is what happened?” Once you have the answer, you then put yourself in the head of the most annoying skeptic and heckler in the audience, the one who’s determined to figure the trick out. That’s your investigator. So as the writer, you get to come up with a magic trick, then you have to outsmart yourself.