In Huber’s second Verity Kent mystery, Treacherous Is the Night (Kensington, Oct.), Verity and her soldier husband, Sidney, are reunited.

Why did you decide to set this series right after the end of WWI?

I’ve been fascinated by WWI and its repercussions for a long time, and I always knew someday I wanted to set a book or series during that period. I was contemplating the nature of marriage during wartime, and the secrets we sometimes keep from those we love the most, when I stumbled upon the idea of making my heroine a Secret Service agent. Once I started researching the era and the roles of women in Britain’s intelligence services, Verity Kent—and her troubled personal life—began to take shape.

Verity and Sidney have become strangers in significant ways after a long separation. Was this theme in your mind from the start?

Verity and the struggles in her marriage were forefront in my mind when I first began crafting the series. The aftermath of WWI is an ideal period in which to examine a marriage in peril. The divorce rate skyrocketed as returning soldiers and the wives and families they’d left behind struggled to readapt to one another. Even those who stayed together lived with the constant strain the war had introduced into their relationships.

How did you research the ruined landscape of Belgium through which Verity and Sidney travel?

It was difficult but intriguing. I drew on photographs of the devastation taken during and after the struggle, memoirs written by survivors of the conflict, travel guides created immediately after the war, even the websites of small Belgian villages. The books written by Capt. Henry Landau about his experiences as head of the military section of the Secret Service’s Rotterdam Station were also invaluable. Part of his job was to establish and coordinate intelligence-gathering networks inside the German-occupied territories.

What drew you to La Dame Blanche, the resistance network in Belgium?

I stumbled across a mention of it while browsing through the history section of the British Secret Intelligence Service’s website and my curiosity was immediately piqued. The more I dug, the more impressed I became. Employing men, women, and even families with children, this group was militarized and brilliantly organized. Few members were ever caught, as the safeguards put in place to insulate each company or squadron kept the entire network from being compromised. Their success, and the anecdotes I gleaned from Landau’s books, made them ideal as a group with which Verity could liaise during the war.