On a freezing November night Commissario Alec Blume is called to the scene of a shooting.

The victim is Sofia Fontana, the sole witness to a previous killing. Blume's inquiries lead from a professor with a passion for the art of memory to a hospitalised ex-terrorist whose injuries have left her mind innocently blank; from present day Rome's criminal underclass, to a murderous train station bombing in central Italy several decades ago.

Against the advice of his bosses and his own better judgement, Blume is drawn ever deeper into the case, which looks set to derail his troubled relationship with Caterina...