A prime number is a solitary thing: it can only be divided by itself or by one it never truly
fits with another. Alice and Mattia are also alone with their personal tragedies. As a child
Alice's overbearing father drove her first to a skiing accident and then to anorexia. When she
meets Mattia she recognizes a kindred spirit and Mattia reveals to Alice his terrible secret:
that as a boy he abandoned his mentally disabled twin sister in a park to go a party and when
he returned she was nowhere to be found.
