1996: Fifteen-year-old Valeska goes on holiday with her mother Monica. Also travelling with her are Jacques, her mother's new boyfriend, and his daughter Lena, with whom Valeska has nothing in common. Slowly, however, a friendship develops between the two girls. But the relationship between the adults gets more and more out of hand. Lisa Brühlmann is currently the most successful Swiss filmmaker internationally. Her feature film debut ‘Blue My Mind’ (2017) won her numerous awards at prestigious festivals. This was followed by commissions in England and the USA and an Emmy nomination for her production of the British cult series ‘Killing Eve’. In ‘When We Were Sisters’, Lisa Brühlmann plays the role of the mother in one of her own films for the first time. She is joined by Carlos Leal as her partner Jacques and the two impressive young talents Paula Rappaport and Malou Mösli as their daughters. ‘When We Were Sisters’ is a sensitively told story about a deep friendship between girls, a complex mother-daughter relationship and smouldering conflicts within a patchwork family.