Maria Mercedes is a poor girl who is abandoned with her brothers and sister by her ambitious mother. Because of the lack of support from her perennially drunk father, she is forced to raise her brothers and sister on her own, working in the streets of Mexico City selling lottery tickets and flowers.
Santiago del Olmo is very sick and knows that he is dying. One morning when he is in the garden, he sees María selling lottery tickets in the street. He comes up with the idea to marry her just to upset his political aunt Malvina after his death as a personal revenge. He gains Maria's trust and friendship, proposes to her, and she agrees. When Santiago dies, María became the head of the family, making Malvina's ire burn stronger. According to his will, Malvina, her son Jorge Luis and her daughter Digna must live there, if they want to inherit any of his fortune. Jorge Luis is a sad man since the murder of his wife on his wedding day. His younger sister Digna is a very religious woman who has never dated a man at all and is afraid of almost every thing, especially her mother.
After María moves into the del Olmo household, she falls in love with Jorge Luis, who is weak against his mother's will and always does as she wants.
Malvina makes it her life's mission to antagonize María. When she finds out that María loves her son, she pushes him to marry her in order to get the money back. She plans that after a few weeks he could make her give him control over the whole fortune and after that get divorced.
Jorge Luis and María get married but they do not share a room nor live like a traditional married couple. Within time, Jorge Luis starts to develop a real and deep love for María. On the other hand, María has another foe, Mistica, a sultry and selfish woman. She used to be Jorge Luis' girlfriend, but then left him heartbroken to marry a wealthy man, Sebastian Ordoñez. She realizes that she still loves Jorge Luis and is furious to know that he is married and falling in love with Maria. She promises herself that she will get Jorge Luis back and starts to help Malvina get rid of María.
María meets Magnolia, a beautiful, rich, and sophisticated woman who is her real mother. Magnolia has now remarried and has another son, but she regrets deeply having left her children. She gains María's trust and starts to help her daughters and her sons, especially Guillermo who is in jail and is the only one who recognizes her. Her true identity remains a secret for María and her other siblings, Rosario and Andres, and all the things she does for them have to be hidden from her new husband, Rodolfo (an architect who is Rosario's boss and is also a friend of Jorge Luis' family) and their son Gustavito (which is a youngest half-brother of Guillermo, Maria Mercedes, Rosario and Andres).
Magnolia teaches María good manners and how to seduce her husband. After Sebastian Ordoñes drops a high class party where he will give a prize to Jorge Luis and then tries to seduce María, Jorge Luis moved by jealousy and by the sight of the beautiful and well-dressed María, finally starts to fall for her and they sleep together. Soon María learns she is pregnant.
After María's father passes away, she and Jorge Luis go on a vacation trip that goes terribly awful because of the intervention of both Mistica and a local lifeguard who hits on María. Jorge Luis makes up his mind and asks María for a divorce as soon as they arrive back to Mexico City. However, Malvina has other plans. She tries to drive María crazy with the help of Cordelio, the butler, and puts her in an asylum. María manages to escape from the asylum and hides from the police in Doña Filo's house, a good friend from her poverty years, until Jorge Luis ask the police not to pursue her any more.
With Cordelio as her ally, Malvina tries to kill María but all fails. Malvina realizes Magnolia's influence and begins to wonder if she could be María's mother. She tells this to her new husband, Rodolfo Mancilla, who in turn goes to María's old house (where Rosario and Andres still live) and asks to see a picture of their mother. He at once recognizes her and later confronts her, arguing with her and throwing her out. Magnolia nevertheless survives by helping out a French tailor who once recognized her talent and pushed her ambitions (which clashed with the need to raise her family; she chose her career over them).
Far from María, Jorge Luis realizes that his feeling for her have grown so strong that he can’t live without her any more. He asks for forgiveness and she returns to the house where they live as a real married couple.
Nine months later María gives birth twin girls, one of which dies a few days latter. Jorge Luis put an end to Mistica's intentions for good after Mistica attempts to pin a pregnancy on him (the child was actually her husband Sebastian's). When he discovers that his mother still hates María, he decides that it is time to leave his mother and raise his family with Maria. He stands up for himself for the very first time against his mother's wishes and leaves. Malvina goes crazy and dresses as María used to in her poverty years and runs to the street where she starts to sell lottery tickets and clean windshields. She is caught and put in an asylum.
Magnolia tells the truth to her offspring. María at first is shocked by this revelation but her resentment shatters and she accepts her mother with love. Rosario is nevertheless disgusted and filled with rancor, a situation that remains until her old boss Rodolfo Mancilla agrees to accept them as his (step-)children. With this, the sisters make peace and Rosario can finally accept the courtship of Ricardo, a younger friend of Jorge Luis', without any remarks by María.
Since María and Jorge Luis only had a civil wedding, they have a great church wedding in the Basilica de Guadalupe with all their friends and relatives, closing the scene after they say "I do" and putting and end to the novella with a romantic kiss.