The trawler Marie-Morgane sinks suddenly and inexplicably with all its crew, including Captain Lenormand and his son. When Nolwenn Lenormand hears the news she's convinced that a submarine on maneuvers must have been responsible.

The trawler Marie-Morgane sinks suddenly and inexplicably with all its crew, including Captain Lenormand and his son. When Nolwenn Lenormand hears the news she's convinced that a submarine on maneuvers must have been responsible. Determined to get to the truth, she decides to investigate the shipwreck herself, so that the case isn't just filed away. But this keeps her from giving her daughter the attention she needs to process her grief. Nolwenn's obsession might cost her what's left of her family. At the same time, the case becomes more complex for Gilles Pezenec, the gendarme in charge, when a fourth body, unknown to everyone, is found on the wreck.—Happy_Evil_Dude