Life seems to smile at Regina Villarreal (Angélica Rivera), a young and beautiful woman who inherits a fortune from her deceased parents. Regina lives with her aunt, Berenice (Norma Herrera), whom she loves as if she were her own mother, her unbearable cousin, Laura (Cynthia Klitbo), and her inseparable nanny, Martina (Josefina Echánove).
Laura envies her cousin and believes that she is more deserving of all that Regina has, so she decides to make her suffer. Laura's first move is to seduce Regina's fiancé, Mauricio (Eduardo Santamarina), who is only after her money. On her wedding day, Mauricio leaves Regina at the altar, a fact which shatters her heart and makes it grow cold and bitter.
Regina moves to one of her properties, "Los Cascabeles" ("The Rattlesnakes"), a ranch far away from the capital. She becomes a resentful and indomitable woman, "La Dueña" ("Lady Owner"), as her employees call her. Furthermore, her reputation earns her the nickname "Víbora" ("Viper") among the locals.
There she meets José María (Francisco Gattorno), owner of the neighboring hacienda "Los Encinos" ("The Oaks"). Both fall for each other, but Regina does not reveal her feelings for him for fear of getting hurt again in a relationship.
Around this time, Berenice, Laura, and Martina also move to "Los Cascabeles". Macario (Salvador Sánchez), the foreman of the ranch, is in love with Regina and he and Laura scheme to keep Regina and José María apart. Laura has fallen in love with José María; because of it, Regina will become once again a target for her cousin, even though this time "La Dueña" will not let anyone steal her beloved's heart from her.
