For anyone who spent several summers avoiding Dan Brown's The Da Vinci Code, Kate Mosse's 2005 blockbuster Labyrinth arrived as a welcome alternative. It was a Grail gripper, but not as we'd known it. Set in a remote corner of the Languedoc, this thrilling adventure featured hokum, heartache and strong female leads. Citadel, the concluding volume of Mosse's French Trilogy, is also her best.
At the heart of the series lies a long-running quest for an ancient Christian Codex – an esoteric manuscript said to contain the power to raise a sleeping army. In Labyrinth it was the 13th-century Cathars who were in need of its help, but in this final instalment Mosse pursues a more ambitious time-line, switching between the story of Arinius, a fourth-century monk, and the tragic history of Sandrine Vidal, an unsung heroine of the French Resistance.
Sandrine is just 18 when she decides to follow her elder sister, Marianne, into the ranks of the Maquis. Coming under the scrutiny of the Deuxième Bureau, she is forced to flee Carcasonne and take refuge in the eerie town of Rennes-les-Baines. It's here that she comes across Audriac Baillard – a semi-sepulchral figure familiar to readers from the pages of Labyrinth. Meanwhile, back in 342 AD, Arinius is also facing testing times. With a sheet of papyrus strapped to his chest, he's heading towards the fortified castellum of Carcaso– a place of safety for Gnostics and Christians braving a new dark age.
Such time-slip narratives can sound flaky in summary, but as a writer Mosse is anything but. Thanks to history's tendency to repeat itself, parallels between the crumbling Roman Empire and the last days of the Reich emerge. Bridging the centuries is Braillard who, with Sandrine's help, is determined to track down the Codex and so end the occupation of the Midi.
Despite a good sprinkling of genre ghoulishness, Citadel is the closest thing to a straight historical novel that the author has yet penned. Fans can expect a passionate finale to a series rooted in a region where history and legend lock horns.