In North Madras (Karuppar Nagaram/Perumparacheri) in the early 1970s, Kabilan is a Dalit labourer at the Madras Port who wants to become a prominent boxer like his father Munirathnam. But his mother Bakkiyam refuses to let him do so, as Munirathnam's fighting prowess led him to be killed in an ambush by a rival gang. Kevin (nicknamed 'Daddy'), an Anglo-Indian friend of Kabilan's father, and who Bakkiyam works for, has been supporting Kabilan's passion since his childhood as his godfather.

In 1975, when Indira Gandhi declares the 18-month Emergency, Rangan, a former boxer, coach and DMK member manages to host a boxing tournament between the Sarpatta and Idiyappan clans.[5] At that tournament, Sarpatta clan faces a massive shock after Meeran, their main bout boxer, gets defeated by Vembuli, a talented boxer representing the rival Idiyappan clan. Afterwards, Rangan announces that he will bring up a prominent boxer to defeat Vembuli the following match, and accepts the condition that the Sarpatta clan would never fight again if they face defeat. Rangan announces that Raman, an amateur boxer will battle against Vembuli, much to the disapproval of the other clan members especially Rangan's son Vetri. Later, Rangan gets dissatisfied by Raman's performance in the training sessions. After Raman insults Rangan, Kabilan, who hears of it, floors Raman black and blue.

Impressed by Kabilan's fighting ability and techniques, Rangan decides to match him up against Vembuli instead. The Idiyappan clan scoffs at the idea of Kabilan as a challenge to Vembuli. After a heated debate Daddy challenges Rose, a legendary retired boxer nicknamed 'Dancing Rose' for his dance-like moves with elegant foot movements, to fight Kabilan. Rose is loved by the crowd and has respect even from the opponents. The upcoming fight soon becomes the talk of the town and the fans dismiss Kabilan as a tomato can. Kabilan manages to defeat Rose, much to the surprise and dismay of the audience. Enraged, Vembuli challenges Kabilan to defeat him in the ring. Raman's uncle Thaniga, who feuded with Kabilan's father in the past, plots against Kabilan for humiliating Raman. He tells Vembuli that he would help him if he is on verge of losing. In the match, Kabilan dominates Vembuli most of the match and almost knocks him out in fourth round. The fifth (last) round starts, but is stopped suddenly as the police come into the venue to arrest Rangan, as the DMK government has been dismissed minutes ago by the Union government and Governor has ordered the arrest of all prominent DMK leaders. Everyone refuses to move until the match ends, and the police wait for the last round to end. The last round resumes, and as Kabilan is to give the final blow to the tired and hopeless Vembuli, Thaniga's goons attacks Kabilan and interrupt the match. Goons attack all the spectators and strip Kabilan naked on stage. The match ends in no result. Rangan and other party members are immediately jailed under the MISA Act. Kabilan is injured in back of head, but recovers.

Kabilan decides to quit boxing after the incident and plans to live a modest life with his mother and his wife Mariyamma. Kabilan and Vetri go to meet Rangan in prison. On the way, the two meet Thaniga as they stop by a restaurant, who provokes Kabilan. In a fit of rage, Kabilan hacks Thaniga's mouth with a sword, he gets imprisoned for six months, though Thaniga survives. In 1978, Vetri Selvan joined the ruling AIADMK, led by Chief minister M. G. Ramachandran,.[6] He and Kabilan initially work under Manja kannan to brew illegal liquor, and eventually start their own brewing business due to Vetri's clout in the party. Vetri, despite growing rich, employs Kabilan as his mere henchman. Kabilan slowly slips into alcoholism which strains his relationship with his mother and his wife.

Rangan is released from prison in 1979 and is disturbed by the changes. Kabilan, now overweight and addicted to alcohol, attends the boxing match between Raman and Vembuli, where the former gets defeated thoroughly. Post match, Vembuli gets challenged by Kabilan and Daddy due to his intentional disruption before. An embarrassed Vembuli accepts but Rangan wants to use another boxer instead, due to Kabilan's lack of fitness and flexibility. However Kabilan stands his ground and insists the fight go on. Vetri asks him to join the liquor trade full time, but is angrily rejected. Kabilan wails to Bakkiyam over the fact that he failed both as a family member and a boxer. Bakkiyam, tells Kabilan to resume boxing to redeem himself. The following day, Daddy sends Kabilan to train under 'Beedi' Rayappan, a fisherman and former legendary Sarpatta boxer. Under Rayappan's guidance he regains his fitness and improves his game. In the match, Vembuli dominates in the early rounds and dislocates Kabilan's left shoulder decreasing his punch power and movements, but Rangan, Vetri, Meeran and other members show up and motivate Kabilan to perform his best. In the final round Kabilan knocks Vembuli out, and the Sarpatta clan gains its prime-match victory after years of failure.