One night in a Parisian hotel, Claire Cousteau, a leading marine biologist with a picture-perfect family life, enjoys an encounter that she thought was her secret. Back home, Claire and her family prepare for their annual long summer in Brittany, and her son Nico asks if his new girlfriend Julie can join them. But unbeknown to Claire’s husband and son, the two women have met before. Under the hot Breton sun, can they keep their bond hidden? Or, will it alter the course of their lives for all time?