Murida lives with her father in the town of Broadfurt, at the foot of an imposing mountain. High up on the mountain rests an old fortress that, many centuries earlier, had been built by fearsome invaders. It has since been converted into a prestigious school for boys. Murida is spirited and fun-loving, but when her father dies, leaving her in the care of an old friend, Isaac Leibniz, her life changes drastically. Isaac lives and teaches at the fortress academy and Murida has to move with him to that imposing fort. Life at the fortress is lonely – women are not allowed inside, so her presence must remain a secret. She finds it difficult to watch the bullying and cruelty experienced by some of the students and uses her time to learn the secrets of the building. An unexpected trip to a nearby town, however, cures her loneliness and thrusts Murida into the centre of a terrifying adventure. The townspeople have been converted to worshiping the cruel god Cromm Cruach. The priests claim that humans must be sacrificed to appease the god and ensure a successful harvest. Murida must face her darkest fears to save the children and help the village to overcome the evil that engulfs it... Inspired by the Krak des Chevaliers in Syria, this is a sweeping tale of bravery and adventure.