Maria Belén is the story of a charming six-year-old girl who has recently lost her adoptive parents in a tragic accident. She was left in the care of her uncle Rogelio, a greedy, heartless man who cold-bloodedly planned the murder of his half-brother Alfonso and his sister-in-law Patricia to inherit their vast fortune. But he never considered the possibility of María Belén surviving the accident, and much less that she would be named the sole heiress of the García Pineda estate. In order to carry out his plans, Rogelio takes her secretly to a boarding school and leaves her there. The only possession Maria Belén brings with her is a little chest, given to her by Patricia, that contains papers and photographs. In it, the child keeps all her secrets and hopes,… and the memory of those happy few years when she lived in the warmth of her parents’ love.

In the course of this moving telenovela, we will discover that Maria Belén’s real mother, Alejandra, died a few days after giving birth, and that her father, Pablo, had to move abroad, not knowing that Alejandra was pregnant with his child.

Ursula, the headmistress of the Brighton Institute, Maria Belén’s new home, is a an embittered spinster who was rejected by Pablo, and in her twisted mind, she blames him for her drab, lonely life. When she discovers that Maria Belén is his and Alejandra’s daughter, she pours out all her resentment on the innocent child, subjecting her to every kind of humiliation and injustice. Only Maria Belén’s vivid imagination, creativity and good heart will help her escape her painful reality.

Upon his return to Mexico, Pablo tries to locate Alejandra, whom he has never stopped loving. The news of her death casts a shadow over his life, and his only ray of hope is to find his daughter; but all his efforts are in vain. In the course of his search he runs into Ana del Rio, a psychologist who offers to help him, and their friendship soon turns into love. However, Pablo feels that he cannot begin a new life until he has found his daughter.

At the boarding school, Maria Belén suffers constantly under Ursula’s relentless hatred, but she also lives moments of great happiness with her new friends: Socorro and Romina, her classmates; gruff old Refugio, who works in a neighboring ranch, and the son of the ranch owner, Bruno, a boy who compensates his loneliness by thinking up wonderful adventures that will turn Maria Belén’s world upside down. But the most wonderful thing of all is the loving bond that will grow between Maria Belén and an old mare called Casilda. A strange empathy will join the destinies of the child and this enigmatic beast, to the point where the events in their lives will mysteriously coincide.

Maria Belén will have to overcome many obstacles on her road to happiness, but her faith will carry her to the end of the rainbow, where she will find a treasure of love.