The film starts with a plane accident in which a small child narrowly escapes. He is then looked after by his maternal uncle, vijayaraghavan and all the family's wealth will be inherited to him. But in the future he should marry a girl whose star is Chothi nashatra (superstitious beliefs) only then will he prosper in life. The boy grows up to be a young man Balakrishnan (Biju Menon), who is unsuccessful in anything he does.
He falls in love with Maya (Lakshmi Rai), the daughter of a wealthy businessman named Patella, who is settled in Mumbai. He then takes her with him and marries her. In the meantime Lakshmi(Baburaj (actor)), a friend of Balakrishnan tries to convince and Balakrishnan's uncle about the marriage and the uncle agrees to visit the couple. But then,on the second day of the marriage Maya leaves him.
Balakrishnan did not want his uncle to know that his wife left him, so he hires a girl Mayamohini (Dileep) to act as his wife. The story continues with many twists and in the later it is revealed that Mayamohini is actually a man named Mohan, Dileep who the Kerala Police had been searching for so long. He had been put into a trap by Patella and his men, who killed Mohan's father to get hold of their property. Balakrishnan agrees to help him in his quest, meanwhile Mohan falls in love with the daughter of a police officer. Later Patella is killed by Mohan.
The movie proved to be a huge success at the box office earning almost 20.90 Crores in 30 days and continued its reign as a crowd puller well into the second month of its release. Mayamohini holds the credit of being the first Block Buster of 2012.