Moondru Mudichu (The Three Knots) is a Tamil film that was directed by K. Balachander. The movie stars Rajinikanth , Kamal Hassan and Sridevi. It is hailed as the movie that made Rajnikanth a big "villain" star. The movie revolves around 3 people - a college going girl(Sridevi) and 2 men who fall in love with her (Kamal Hassan and Rajnikanth).

Kamal Hassan and Rajnikanth are room-mates in a city. Kamal Hassan falls in love with Sridevi who lives in the same apartment complex. Rajnikanth, who has his eyes on Sridevi, pretends to back Kamal Hassan's love while secretly hoping to create a divide between them. Sridevi realizes Rajni's evil intentions when she finds out that he has seduced an innocent girl living in the same apartment complex. However, she is unable to convince Kamal Hassan, who hero-worships Rajni.

Things come to a head when Kamal and Sridevi go for a picnic by the lake and Kamal decides to invite Rajni along. As the three of them head to the middle of the lake on a boat, Kamal topples over by mistake. Rajni refuses to jump in and save Kamal, on the pretext that he does not know swimming. A devastated Sridevi returns home to another shock - her sister, who plays small time roles in the movies, has suffered from a fire accident which has left her face permanently charred. Overnight, Sridevi's life undergoes a drastic change.

In an attempt to salvage her life, Sridevi decides to marry an old widower who needs someone to look after his children. One of his children happens to be Rajnikanth. Sridevi goes ahead with the marriage despite this. After her marriage, she decides to use her 'mother' status to exact revenge on Rajnikanth.