Cotton Malone has recently retired from the US special forces, to pursue his dream of running an antiquarian bookshop in Copenhagen. But when his old boss is attacked on a visit, Cotton is dragged into an extraordinary mystery - a mystery that centres around an old book, which many people seem to want, and which has already cost several lives. The book seems to point towards a connection with the Order of the Knights Templar, once the most powerful organization in the whole of Europe - apart from the Church itself - and wiped out in the 14th Century.

Meanwhile, at an ancient abbey in the Pyrennees, the old Master is dying, and his deputy faces an unexpected challenge to succeed him. Someone wants to restore the Order to its former glories, to rekindle the secret it has held for centuries...

Cotton and his friends must crack the codes and swerve dangerous pitfalls as they race towards a secret so explosive it could change the world.