In 1519, a Mayan priest, Ahzac, discovers that his daughter Ixmy has fallen in love with a white foreigner. He plans to sacrifice her as a gift to the gods, along with items made of gold and a black pearl. Ixmy avoids her fate, and Ahzac curses the black pearl: "Whoever has this pearl in their possession will never be able to know what happiness is!"
In 1987, Eliseo Bravo and Hernán Lazcano explore the coral reefs of Cozumel and discover the black pearl. When Hernán touches the pearl, Ahzac's curse takes effect. Eliseo's greed leads to Hernán's death, leaving his wife Analy to raise their newborn daughter Aymar alone.
Nineteen years later, Aymar Lazcano is a beautiful young woman. Aymar meets and falls in love with Nicolás Bravo. After her mother is murdered by a jealous old suitor of hers, Aymar lives with a family friend Pablo Solis.
Avaricious Maura Duran meets the main characters in the guise of Karina Rosemberg, a rich heiress whose land Eliseo covets. Manipulated by Maura, Eliseo detests Aymar and her relationship with his son and Maura falls in love with Eliseo's oldest son David.
The real Karina Rosemberg was crazy because she saw her parents burned alive. She was in the care of an old man who found her wandering. Unfortunately he died and afterwards Aymar took care of her.. Karina had met David and fallen in love with him, despite his drunkenness at the time, but he does not reciprocate her feelings because he is infatuated with Maura. Maura's attempts to separate Aymar and Nicolás include a fake pregnancy (with Nicolás, the alleged father), an attempted murder and the killing of Nicolás' youngest brother, Leonardo.
Sirenita who is the real Karina Rosemberg decides to run away from home because David confesses his love to someone else. She meets a kind women who helps her get over her feelings for David by giving her a makeover and teaching her manners.
At the end of the series, Maura is stung by a swarm of bees and dies of anaphylactic shock. David and Karina and Aymar and Nicolás marry, and both couples are happy – Nicolás and Aymar with their son Hernán Nicolás Jr. and their nephew Leonardo; and Karina and David with their son Elisèo David.