Mlada uspešna pevka Cléo tava po Parizu od 17h do 19h in čaka na rezultat testa za raka na želodcu. V dveh urah se njeno življenje popolnoma spremeni, ko se bori z občutkom smrtnosti in mora vnovič ovrednotiti svoje življenje. Cléo (Corinne Marchand) je mlada, čedna in ponavadi brezskrbna pevka z mnogimi uspešnicami, ki napeto pričakuje rezultate nedavne biopsije. Skrbi jo smrtna diagnoza raka in njeno doživljanje iz panike prehaja v samozavest ter iz upanja v obup. V poldrugi uri, ko zabija čas pred obiskom pri zdravniku, hodi po ulicah Pariza ter srečuje prijatelje, ljubimce, glasbene kolege in naključne ljudi. Kljub temu je osamljena, dokler ne spozna vojaka na poti v vojno v Alžirijo. On je edini, ki z njo deli negotovost in strah pred svojo usodo.
Two hours from 17:00 to 19:00h on the longest day of the year in the life of a young Parisienne is presented. Florence Victoire, who is better known by her stage name Cléo Victoire (as in Cleopatra), is a singer with three hit singles to her name, and as such some renown. Two days ago, she went in for some tests for abdominal issues to see if it is cancer. She will be getting the results today at 18:30h. She is certain that it will be a terminal cancer diagnosis, her mind fixated on that outcome and what it actually means. This belief affects how she approaches the day, from her encounters with friends and acquaintances to what she observes in total strangers around her. It could be as simple as how she views the lyrics to new songs presented to her from her songwriting team, to her feelings about a conversation she overhears in a café between a couple having relationship problems, to the typical sweet nothings spoken to her from her lover, José. There are certain things that do temporarily take her mind off of waiting for the test results, but something will always bring her back to that as the issue of her day. It isn't until just before she is ready to call the doctor that she may get a different perspective of the day and thus her life in a chance meeting with a stranger named Antoine, a French soldier at the very end of a three week leave from the Algerian War.