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, Cotton is dragged into a mystery that centres around an old book, which many people seem to want, and which has already cost several lives. The book is connected with the Order of the Knights Templar, once the most powerful organisation in the whole of Europe, apart from the Church itself. Meanwhile, at an ancient abbey in the Pyrennees, the old Master is dying, and his deputy faces a challenge to succeed him. Someone wants to restore the Order to its former glory, to rekindle the secret it has held for centuries. Cotton must crack the codes and avoid dangerous pitfalls as he races towards a deadly secret.