Maite is devoted to her daughter Nerea and the lobster hatchery she runs, but her world is shattered when Nerea announces that she will go to study in Barcelona.
Consumed by the fear of abandonment and coinciding with the appearance of a strange crab in the nursery, Maite begins to lose control of her world. In a desperate attempt to keep her daughter, she kidnaps her and locks her in a replica of her childhood bedroom.
Nerea, determined to free herself, manages to poison her mother knowing that she is allergic, forcing her to choose between clinging to her obsession or letting her go to save her.