Almost Nothing Happened

One long summer of nothing. 48 hours of everything. It is the hottest weekend of the year in Paris. Seventeen-year-old Callum is waiting for the Eurostar home at the end of a French exchange - a whole two months in the countryside in which he barely spoke any French, made zero friends (except a dog) and did not experience a momentous sexual awakening. Nothing happened. Just as the train is about to leave, his phone rings.
Callum must choose : What if he doesn't catch the train home ? What if he just switches off his phone and walks out into this strange city ? What could possibly happen, after two months of nothing, in just forty-eight hours ?