Of all the relationships in the world, the relationship between husband and wife is the greatest. The film tells the truth that if it doesn't go well, a third man will enter the life of two people. Moondram Manithan is a murder thriller. The story unfolds on screen as police officer K Bhagyaraj watches a student stand as the topper in the state in his final school examination.
Bhagyaraj comes to investigate the murder of police inspector Rishikanth. There are some truths in it. Director Ramdev has played the role of a drunkard. Unable to reconcile with the drunkard, wife Prana is the mother of a son and makes him study by doing housework.
Rishikanth and Sonia Aggarwal are husband and wife in the house where he works. Rishikanth, who is a police inspector, and Sonia seek the help of a friend to resolve their ego problem. He keeps an eye on Sonia and sexually assaults her. In the ongoing investigation by K. Bhagyaraj, we are shocked to know who killed Inspector Rishikanth. K. Bhagyaraj completes that shocking climax with his resilient judgment.
