Martha lives in a rural apartment on the outskirts of Madrid and spends most of her time alone while her husband, Carlos, travels for business. One day, Martha notices heavy footsteps from the apartment above. Her neighbor, Julia, faces a similar situation with her husband, Victor, also away. Martha's suspicions are aroused when she overhears Julia's explanations for Victor's absence, leading her to suspect foul play. Determined to uncover the truth, Martha begins her investigation.