Felipe and Diana have always loved each other, but in their past lives this love ended in a terrible, tragic way. Destiny, or whatever it's called, reunites them again in Mexico City in the year 2005. Felipe is a young university instructor unhappily married, with a son, and of course with a lover. His wife convinces him to consult a psychiatrist, who turns out to be Mariana, the woman that he constantly sees in his dreams and nightmares, also turning out to be one another's great love in their past lives. The story takes place mainly in today's era and goes back to the existences of the characters' past through each others dreams, and through the means of hypnosis. Little by little Felipe and Mariana will discover their "true" stories and all the truth about the people that surround them until they can again unite the two halves of the sun.