Manikam is a humble auto-driver who lives in Madras with his mother Vijayalakshmi, brother Shiva, and sisters Geetha and Kavitha, and would go to any extent for their well-being. He gets Kavitha married to her boyfriend, who is from an affluent family. Shiva manages to become a sub-inspector. On seeing Manikam's photo, DIG Dinakar, who interviewed Shiva, wants to meet Manikam. Manikam hesitatingly comes to meet Dinakar in his office. Dinakar suspects Manikam's identity. Geetha gets admission in a medical college, but the chairman asks for her carnal company in return for a seat. Manikam interferes and tells the chairman something behind closed doors that Geetha cannot hear, after which the chairman unconditionally gives Geetha a seat.

Meanwhile, Priya travels in Manikam's auto frequently and develops a liking towards him seeing his good character. Priya discovers that her father is a smuggler and decides to maintain a distance from him. Priya proposes her love to Manikam but Manikam does not initially accept as he learns she is the daughter of Kesavan (with whom Manikam has a past history) but eventually does so.

Indiran is a gangster who uses his henchmen to collect "commission" from all business owners. When Shiva beats two of Indiran's henchmen who attacked a man for not being able to pay commission, Indiran tells Shiva that he runs that area and his laws apply. Shiva and Indiran's fight is stopped by Manikam, who requests Indiran to beat him and spare Shiva. Manikam is tied to a pole and severely beaten by Indiran, but bears it for the sake of his brother without retaliating.

Later, Shiva again takes action against Indiran by submitting an arrest warrant which makes him furious again. This time after his release from jail, Indiran kidnaps Geetha and tries to molest her in front of the public. To everyone's surprise, Manikam hits back Indiran and his men, thereby saving his sister. The beating of Indiran and his henchmen is so severe that it shocks Shiva. He confronts Manikam about his activities in Bombay, where he lived previously, but Manikam does not respond.

It is revealed that, a few years before, Manikam lived with his parents in Bombay while his siblings were studying in Madras. Manikam's father Rangasamy was an honest man, but was employed with gangster Mark Antony, as Rangasamy helped Antony during the initial days, which made him to stay loyal to Antony for life. Manickam and his friend Anwar Baasha were protesting against the ridiculous behaviors of Antony's men, which prompted Antony to kill Anwar; Manikam was spared as he is Rangasamy's son. Enraged, Manikam decided to take the same path to destroy Antony and had killed Antony's hitmen to avenge Anwar's death.

Manikam received the support of local people in Bombay who feared for Antony, where he transformed himself into a gangster named Manick Baashha and had frequently interfered in Antony's illegal activities which created enmity between the two. Baashha's command over the city had increased, where Antony decided to kill Baashha, but Baashha escaped from Antony's plan. Enraged, Antony killed Rangasamy, prompting Baashha to help the police arrest Antony while Kesavan (who was Antony's henchman) killed Antony's family and inherited his business and wealth. Before dying, Rangasamy requested Baashha to return to Madras and start a peaceful life. Baashha assented, faked his death and secretly left to Madras along with Vijayalakshmi.

After remembering his past, Manikam learns that Kesavan has arranged Priya's wedding against her wishes, where he arrives to the wedding hall to stop him. Kesavan is shocked to see Baashha alive in the form of Manikam. Frightened, he permits Priya to go along with Manikam. On learning that Baashha is alive, Antony escapes from prison, kills Kesavan for betraying him, and also kidnaps Manikam's family members, where he threatens Manikam to surrender failing which his family members will be killed. Manikam rushes to the spot, fights Antony and his gang and also saves his family. He nearly kills Antony, but is stopped by Dinakar. Antony then steals Dinakar's gun and tries to shoot Manikam, but is shot dead by Shiva from behind.