On the high seas, a sailor is murdered on a Swiss merchant navy cargo ship. Aurélie Mercier, a former inspector transferred to the municipal police, returns to duty and goes to Cape Town to repatriate Florian, a suspect who is accused by everyone. He proclaims his innocence and says he is looking for Julia, his girlfriend.

An unexpected witness gives a new twist to the investigation, while a strange crate must be transferred to a ship in distress. For Aurélie, each answer leads to more questions and, as she seems to be getting to the truth, a new tragedy looms...