HC: Youâ??re known for writing historical adventures set in France, but what I love about your stuff â?? and what we perhaps both have in common â?? is an obsession with the past haunting the present. Why are you drawn to this theme?

KM: 'Haunting the present', that's absolutely it. The decisions made, the mistakes, the violence of the past cast a long shadow and those affect the way people generations later behave. In the south of France- which was occupied from November 1942 to August 1944- that shadow is still there. In some villages, people still walk past the closest bakery because it's owned by a family who informed on their neighbours during the war. In Carcassonne itself, many of the main streets have been renamed in honour of resistance fighters. I knew that the date of death on each sign was the same - 19th August 1944. I became obsessed with finding out what had happened on that day. Over time, the men who died then have been identified, but on the monuments are written words that haunted me for years and were the inspiration for Citadel: 'And Two Unknown Women'. Even after years of research, I never discovered their names. But I knew I could write a novel about the sort of women they must have been - courageous, exceptional. That determination to honour the sacrifice of those unknown women led to Citadelâ??s protagonist Sandrine and her all-female band of resistance fighters.

HC: Citadel is your first novel set during World War Two. I know you love suspense so how do you create it when, well, we already know the outcome?

KM: I do love suspense! Much of my reading for pleasure is crime fiction. I love a puzzle, love the business of pitting myself as a reader against the author's imagination. It's tricky, especially with World War II. But of course in adventure writing, as in crime, it's how you get there that matters. The key ingredients in adventure writing are momentum, jeopardy and emotion. Developing the characters and working out the twists and turns of the story are easily as important as the climax itself. That's what I love about writing, working it all out.

HC: Hereâ??s a research question: What was the most extraordinary story you uncovered? More to the point, what do you do when you run across great research but it wonâ??t fit into the story?

KM: I am a novelist, not a historian, and I hate the idea of 'stealing' someone's real life. I don't want to write a thinly-veiled version of a real person. Iâ??d rather use my research and imagination to create convincing characters who might have been. So, this is a roundabout way of answering your question. I wanted to protect the identities of people who were generous enough to share their stories with me, or the stories of their parents and grandparents. For example: the woman who showed me the trap door in the floor of their restaurant where they had sheltered Jewish children before smuggling them across the border to Spain; the son who showed me the bullet holes in the wine vats where Resistance fighters hid; the marks in the ground where the signs for the Jewish internment camps â?? whose existence was denied for years - are still visible. So many incredible, dreadful, stories that would have been wrong to include. But the emotion of those stories is in Citadel and the fears, loves, pride, honour of those people appears, I hope, in some of my characters.

Harlan Coben is the bestselling author of sixteen previous novels, including the #1 New York Times bestsellers "Long Lost" and "Hold Tight. " Winner of the Edgar Award, the Shamus Award, and the Anthony Award, Coben lives in New Jersey with his family.