Stranger.by.the.lake.aka.l.inconnu.du.lac.2013.... <UPDATED ⟶>

The story revolves around Franck (played by Jérémie Renier), a police officer who spends his free time swimming at a secluded lake in the French countryside. One day, while he's at the lake, he witnesses a murder. The killer, a stranger (played by Christophe Bouquet), then approaches Franck and engages him in a conversation.