Masters of psychologically complex detective stories, the mother-son team of Caroline and Charles Todd, who write under the name Charles Todd, have gotten consistent raves from reviewers over the past decade for their series of intense, crafty whodunits, but their sales have not matched their critical acclaim. Now, after 11 books featuring Insp. Ian Rutledge of Scotland Yard (including this year's A Matter of Justice, Morrow), the pair hope that will change with their new series, also set, like the Rutledge series, against the background of WWI, featuring a very different investigator: army nurse Bess Crawford, who debuts in A Duty to the Dead, due from Morrow.

The Rutledge books are notable for the presence of an original sounding board for the detective, the ghost of Hamish Macleod. In the hell of the trenches of France, Rutledge ordered Hamish, his sergeant and subordinate, shot when he refused to lead his men into inevitable slaughter. Rutledge returned to England suffering from what is now called post-traumatic stress syndrome and is regularly haunted by Hamish. The dialogues he has with Hamish place Rutledge in fear for his sanity, even as Hamish's reactions to witnesses and events help guide Rutledge to the truth.

Caroline and Charles, who live in Delaware and North Carolina, respectively, and come together in Delaware for work, decided it was inconceivable that Rutledge would return unscathed after four years in the trenches. He couldn't return to duty with a serious physical injury, so they hit upon having him suffering from shell shock. “The solution was to have him—like so many soldiers—wondering why he lived and others died. Hamish becomes a focus for all the young Scots that Rutledge had to lead into battle day after bloody day and watch die,” Charles says.

“Hamish knows only what Rutledge knows, sees and hears,” Caroline says. “But there are many things we know and don't realize we know. There are things that once put together make perfect sense, but in their separate pieces don't seem to fit. That's the role of our subconscious mind, or whatever runs the shop while we are busy elsewhere.”

The Todds are not the most obvious candidates to write about the psychic scars of the battlefield. Charles, whose cleverness is evident when asked how old he and his mother are (“A gentleman never asks or answers that question about any lady, not to mention your mother”), was a corporate trouble-shooter, and Caroline earned a graduate degree in international relations. But the credibility of their depiction of war trauma is demonstrated powerfully by their strong fan base among Vietnam veterans. Caroline and Charles have spoken to war veterans who offered their own perspective on the reality of PTSD. And Charles says, “What surprised us most, once we'd decided that Rutledge's shell shock would take the form of a dead man's voice, is that many veterans were very familiar with talking to the dead. One man told us he talked to his WWII buddy nearly every day, even now.”

As with much of their writing career—the first Rutledge, A Test of Wills (1996), was submitted to St. Martin's without an agent—there was a strong element of serendipity in the creation of Bess Crawford. According to Caroline, “While traveling with friends in England, in Kent, that eye for a setting that we've trained so well began to pick up places that seemed made for scenes to happen, and yet we'd been in Kent with Rutledge. Our friends suggested that another character was trying to get our attention and that it should be female. We started playing around with ideas, and voila! We had a story.”

Crawford, like Rutledge, is motivated by guilt. While serving as a nurse, she promised to deliver a message for a dying soldier, but never did. The Todds write about her in the first-person, because, Caroline says, “You see things differently first-person. In first-person, you can only know what Bess sees or hears or feels. And she can be mistaken sometimes because she herself must draw on what she's heard or is told or sees for herself. And that can sometimes be a half-truth.” With Morrow planning on publishing one Rutledge and one Crawford a year, the Todds will have plenty of opportunities to explore the deceptions of others and of one's self after the battlefield guns have fallen silent.