Red herrings are the natural enemy of the crime thriller viewer, particularly when the show is supposedly encouraging you to guess the killer yourself (something the show-makers admitted in the first season), and when they don't have an explanation, it's frustrating. When Lee and Claire faced off for some sex/a fight in the sea, the femme fatale made a seemingly throw-away comment about there being someone in France who knew Lee. It was clearly supposed to be a misdirected clue that Lisa was still alive, but then there was absolutely no explanation of what she meant, so the red herring feels like an unresolved point.