The story begins with a fight of the female boxer Esperanza Muñoz—nicknamed "Monita"—who has injured her hand from fighting. Her manager, Enrique "Quique" Ferreti, is pressuring her to continue fighting despite her pain. This injury complicated her economic situation, as her boxing provides the only income for her adoptive family, namely Quique and his mother, Maria de los Nieves, who loves Esperanza like a daughter and won't stop at nothing to get her to marry Quique. Her neighbor Kimberly suggests that Esperanza applies for a job in the Quesada Group, where she works as a janitor, but the secretary Mercedes rejects Esperanza due to her brutish attitude as well as the way she was dressed. Martín Quesada, president of the company, sees Esperanza crying in the street and hires her as his personal assistant. Through one of his company's foundations that provides shelter to poor children, Martín also meets three orphan siblings who opposed being adopted by different families, and, partly influenced by his desire to start a family, and part encouraged by Esperanza, he takes them into his home and starts the legal proceedings to adopt them. Martín begins to like Esperanza, but his girlfriend Constanza, a cold, manipulative and malicious woman, is wary of her and sees her as a threat to her goal of getting Martin to marry her so that she can partake in his fortune. Esperanza is in a relationship with her manager Quique, but she does not tell Martín about it, instead pretending he is her brother, mostly out of shame, but also because she doesn't want to hurt Quique's feelings for her. She also hides from Martin the fact that she is a boxer. Unbeknownst to the other characters—including Martín and Esperanza—Quique and Constanza began their own arduous relationship. Martín breaks off his relationship with Esperanza when he sees her goodbye kiss with Quique, and Martín realizes that she was lying to him.