The search for answers about her friend's death leads Lucía to a park in Alcorcón, where a chance discovery in a bush reveals a dark blue velvet box. Inside, a photograph fragment of an elegant man in white moccasins raises the unsettling question of his connection to the tragic events.

The protagonist hesitates between going to the police or seeking the truth alone, fearing disbelief. She senses the key lies with her mother and a missing photograph, deciding to travel to the sierra de Madrid to confront her.

In the park, an enigmatic man dressed in grey, whom Lucía recognizes from the previous day, reveals that her mother did not keep a promise and that her destiny is sealed. After he leaves in a taxi, Lucía heads to her mother, Teresa's, house in the mountains.

During a tense conversation, Lucía shows her mother the moon-shaped earrings, triggering a shocked reaction. Teresa reveals that the deceased friend, Ana, was actually her twin sister, and that the earrings belonged to their mother, a gift from their father on her wedding day.

Teresa, the elder sister of Lucía and Ana's biological mother, confesses to having cared for the girls, regretting that she could not prevent Ana's tragic fate. The news leaves Lucía devastated as she realizes her friend was her sister.

The story concludes with Lucía asking about her biological mother's death, leaving the resolution of this complex family entanglement unresolved.