Roxana Aubrey decides to drop her studies and escape her life in Paris for a free diving course in the south of France. She is quickly pulled into a life that reaches new depths brought by the weight of an ocean's descent.

The Section de recherches is a special unit of the Gendarmerie nationale, responsible for the most complex cases. In Bordeaux (from 2006 to 2013) and then in Nice (since 2014), child abductions, disappearances, heinous or sexual crimes are the daily lot of the investigators in this research unit. In the search for witnesses, the team is authorised to extend its investigations beyond France's borders.