"A prime number is a lonely thing: it can be divided only by itself, or by one; it never truly fits with another ... Alice and Mattia are alone. Alice bears the scars of a skiing accident that nearly killed her, and Mattia lives with a guilty secret that lies at the heart of his disabled twin sister's disappearance. They each recognize in the other a kindred, damaged spirit - their destinies seem irrevocably intertwined. But when Mattia accepts a mathematics posting that takes him thousands of miles away, it seems that love might just be a game of numbers after all; until a chance sighting by Alice of a woman who could be Mattia's sister forces a lifetime of hidden emotion to the surface. "--Publisher description.