Carolina and Eva Villanueva board the Bárbara de Braganza, a luxurious ocean liner connecting Vigo with Rio de Janeiro. On the first night, Eva witnesses a murder: a woman falls overboard. The two sisters decide to investigate on their own, with the help of the ship’s first officer. Not only will they put their lives at risk, but in their pursuit of the truth, they will uncover a mystery that hits very close to home.