Pablo is a young, wealthy but solitary man traumatized by a fatal car accident. He meets Lara through a dating app tied to an exchange of the titular blue box. As their relationship grows, Lara draws Pablo out of his shell. But an anonymous warning alerts Pablo that Lara may not be all that she seems. What begins as an intimate connection gradually turns into a tense psychological game of cat and mouse, forcing Pablo to confront both his past and the true nature of the woman he is falling in love with.

因被指控杀害弟弟，萨尔瓦多独自生活在巴塔哥尼亚中部。几十年后，他的另一个弟弟马科斯携妻子，说服他出售祖产，分享遗产。随着事情发展，受害者和凶手角色不停地变换。