She joins forces with , an expert in medieval fortifications, to solve a riddle hidden within the stones and mason marks of Spanish castles. The duo must stay ahead of art thieves, unscrupulous hitmen, and ambitious millionaires in a race across Spain to uncover one of history's greatest secrets. Key Details

is a fast-paced thriller by Spanish author Luis Zueco , originally published in 2012 and re-released in 2025 . The novel blends contemporary mystery with historical enigmas centered on medieval castles and rare manuscripts. Plot Summary

The story follows , a quiet worker at the Spanish National Library who collects old books. Her routine is shattered when she discovers a mysterious manuscript within an ancient book, revealing a secret that puts her life in danger.