A baffling discovery shakes Ludwigshafen: on the misty banks of the Rhine, a mother and daughter discover the body of a young man - yet when the police arrive, the deceased has vanished. Inspector Lena Odenthal faces a mysterious case, for the man presumed dead had only recently crossed her path as a witness in a drug investigation. As she picks up the trail of a mysterious figure known as "Mother," she has no idea that she is thereby putting her own life at risk…