The film is also known as The Beating of the Butterfly's Wings, a literal translation of its original French title, Le battement d'ailes du papillon.
Audrey Tautou plays shop assistant Irène, who on the way to work takes a seat on the Paris metro opposite an older woman who tries to interview her for a marketing survey.
After she leaves the metro, a young man sitting alongside (Faudel) tells the older woman he was born on the same day and asks her to read the rest of the horoscope.
The film then traces a range of characters of diverse ages, ethnicities and social status whose daily lives intersect with Irène and Faudel's in a variety of ways and come together at the end of the day.
Seemingly trivial events—such as the throwing of stones or a shoe, the theft of a coffeemaker, a pigeon's consumption of a macaroon—determine the decisions and lives of the many characters.