Physical laws and human relations. In Terni (in the center of Italy), during a hot summer, Matteo, 30-years old with a degree in physics but unemployed gives private lessons to Elsa and Giulio. The three of them soon become friends but Matteo and Giulio also become love rivals.

A teenage girl spending the night at the place of a boy she likes finds herself targeted by a mysterious serial killer who may be the very boy she is with.