Burgos, Christmas Eve, 1257. Princess Kristina Håkonsdatter of Norway arrives in the city on her route to Valladolid to marry Alfonso X the Wise, as his wife was unable to produce a male heir to the Castilian throne.Eight hundred years later, Carlos Lafuente, a researcher from Montanilla University is asked to prepare report regarding a manuscript discovered near the Silos monastery.Wit h the assistance of Arthur Trevelyan, a post-graduate student, and Elena, a colleague paleographer, he will investigate the dark clues he discovers. Most of the time, he will just go with his gut.From that point forward, the present and the past appear to entangle like invisible knots, which Arthur prefers to call "significant coincidences" and which will lead the small group of researches to an unexpected conclusion. The investigation will take them to Covarrubias and then to Burgos, in quest of the hidden secrets that reside in Las Huelgas monastery, as well as in the city's cathedral.