In 1988, the slum of Dharavi in Bombay (now Mumbai) are ravaged by riots between the local Maharashtrians and the immigrant Tamilians following the death of Dharavi\\\'s Tamil mafia don Varadarajan Mudaliar. A Tamil coolie named Ramadurai (Sathyaraj), known as Anna among the locals, bravely fights the Maharashtrians and also encourages his fellow Tamilians to fight them. As a result, his wife Ganga (Rekha) is killed by the henchmen of the Marathi leader who instigated the riots. In retaliation, Ramadurai kills the Marathi leader following which he decides to step into Varadarajan Mudaliar\\\'s shoes and protect Dharavi. He then gives away his young son Viswa to his friend Ratnam (Nassar) as he wants him to grow up away from the Bombay underworld.
25 years later, Ramadurai has established himself as a mafia don, providing his own brand of justice to protect the downtrodden and engaging in a bitter feud with the gang led by Bhima Bhai (Abhimanyu Singh), the son of the slain Marathi leader who has sworn to take revenge on Ramadurai for killing his father. With support from the Government of Maharashtra and the Mumbai police, Bhima Bhai manages to frame false cases against Ramadurai and his gang, as a result of which Ramadurai goes into hiding.
Meanwhile, Viswa (Vijay), who is now an adult, lives in Sydney and runs a mineral water bottling plant, assisted by his childhood friend Logu (Santhanam). He maintains contact with his father regularly, though he is oblivious of his activities in Mumbai. While driving one day, he runs into a young woman named Meera Narayanan (Amala Paul) and immediately falls in love with her. He pursues her till her house, where her father (Suresh) takes an immediate liking to him. Soon, Meera reciprocates Viswa\\\'s feelings for her and together they revive her father\\\'s unprofitable restaurant business and win a local dance competition. Eventually, she proposes to Viswa and expresses her intention to meet his father. When they arrive in Mumbai however, they are received by Ramadurai\\\'s assistant Ranga (Ponvannan), who takes only Viswa with him to Mahim Fort, where he finally meets his father after many years.
After hearing his story, Ramadurai decides to meet Meera and her father at their hotel to finalise the wedding. It soon turns out that Meera is a police officer who knew that Viswa was Ramadurai\\\'s son and she along with another police officer (who pretended to be her father) decided to lure him to Mumbai to arrest his father by faking her love for him and pretending to show interest in meeting his father. Ramadurai is arrested, but as soon as he is locked in the police van, the van explodes, killing him. Viswa, who is also present, notices that the van was bombed by Bhima Bhai and his gang.
A distraught Viswa refuses to return to Australia and instead takes charge of his father\\\'s gang. After stopping a Bhima Bhai-led eviction drive in Dharavi, he is arrested and brutally beaten by the police, only to be released after Meera intervenes. However, his resilience and attempt to stand up to Bhima Bhai makes him a hero among the downtrodden and is hailed as the successor of Ramadurai.
Later, clashes between Maharashtrians and non-Maharashtrians take place at Matunga. Video Kumar (Udhaya), who is video recording a Gujarati wedding there, finds out that Bhima Bhai and his henchmen are responsible for instigating the riots in order to lure Viswa there and kill him. He records their conversation, but is immediately noticed by them, who pursue and kill him. However, they are not able to steal the tape where their conversation was recorded as it had been stolen from Kumar while he was escaping from them in a local train. Viswa finds out about the incident and immediately tracks the pickpocket who stole the tape, acquiring the tape much before Bhima Bhai and his henchmen acquire it. When the tape is made public, Bhima Bhai is arrested.
Some days later, at the Maha Shivaratri celebrations at Dharavi, Viswa and his men get drunk. The next morning, he realises that six of his men, along with a young Gujarati woman Gowri (Ragini Nandwani), who had a crush on Viswa, were killed the previous night while he was drunk. He also finds out that Ranga has been kidnapped by Bhima Bhai, who has escaped from prison and is keeping him prisoner in a fort. He immediately rushes there, only to find out that Ranga was working for Bhima Bhai all along.
Ranga had killed Viswa\\\'s henchmen when Viswa was drunk and also killed Gowri after she saved Viswa from being killed. He stabs Viswa and escapes with one of Viswa\\\'s henchmen (who is oblivious of Ranga\\\'s double agent role). After finding out that Ranga had killed Viswa and was a traitor, he dashes the car they are in into an oil truck, killing them both. It is then revealed that Viswa did not die as claimed by Ranga, but is still fighting Bhima Bhai and his henchmen at the fort. After subduing all the henchmen, he finally stabs Bhima Bhai in the neck, killing him. Soon, Meera arrives there with the police and after finding out that Viswa killed Bhima Bhai and his henchmen, she shoots their dead bodies to show that she killed Bhima Bhai because she has now fallen in love with Viswa as a result of which she doesn\\\'t have the heart to arrest him. She then resigns from the police.
The movie ends with Viswa and Meera getting married. Also, the surviving members of Bhima Bhai\\\'s gang, unwilling to face Viswa, flee Mumbai.