An ambulance driver, medical broker, hospital worker and a surgeon are abducted at dawn, which is traced to Dr. Maaran, a doctor from Chennai, who is known for providing treatment to all at just ₹5. Maaran is arrested and interrogated by Inspector Ratnavel "Randy", who is assigned the case. Maaran explains that the four were responsible for the death of an auto driver's daughter and subsequent suicide of his wife due to their greed for money and negligence in providing proper healthcare. He gives Randy the locations of his hostages, but asserts that they can be saved only if they are taken in time to hospital just like the auto driver's daughter. Maaran reveals that he is not Maaran but his doppelgänger Vetri, a magician.

Vetri was also responsible for the death of Arjun Zachariah, a corrupt doctor who was killed during a stage performance in Paris two years ago. Daniel Arokiaraj, another corrupt doctor and the head of the state's medical council, sees Maaran's inexpensive healthcare as a threat to his flourishing hospital business and decides to kill Maaran using his goons but is saved in the nick of time by Vetri, who knocks Maaran unconscious and swaps places with him, providing clues to the police which led to his arrest. Maaran is rescued, while Vetri, manages to escape from Randy. Later, Maaran confronts Vetri, believing him to be the cause of all his problems. Vadivu, Maaran's compounder, and also Vetri's assistant, intervenes and explains to Maaran why Vetri is targeting doctors indulging in corrupt medical practices.

Past: Maaran and Vetri are the sons of Aishwarya "Aishu" and Vetrimaaran, an altrustic village wrestler and chieftain. Vetrimaaran decides to build a temple in his area and holds a large festive event. However, a fire breaks out, injuring many and killing two children due to lack of mobility. On the advice of Aishu, Vetrimaaran establishes a hospital in his village Manoor in Madurai with Daniel and Arjun as chief doctors, while Vetrimaaran manages the hospital. However, it soon turned out that Daniel and Arjun are money-minded misanthropists and performs a Caesarean section on Aishu, when she was in labour with her second child (Vetri) to extract more money from Vetrimaaran.

With an overdose of anaesthesia and loss of blood, Aishu dies while the child was declared as stillborn. When Vetrimaaran learns about this, he confronts Daniel, but is attacked. Vetrimaaran fights the henchmen, but gets stabbed to death by Daniel's assistant Kasi, where Daniel reveals that he was the mastermind behind the fire accident in the temple so that Vetrimaaran could build a hospital for their business profits. After having killed Vetrimaaran, Daniel and Arjun embezzled money in medical service to consolidate their dictatorship over the years, while creating a massive genocide from beyond.

However, Maaran is saved as Vetrimaaran has placed an unconscious Maaran (who had been struck on the head with a glass bottle) safely on a truck, but loses his memory and is unable to recollect anything that happened before passing out. Meanwhile, Vetri miraculously survives, and their paternal uncle (Vetrimaaran's younger brother) Vadivu takes care of him. Vetri and Vadivu are adopted by a famous magician Salim Ghosh, and Vetri soon learns all the magic tricks in order to exact vengeance.

Present: Upon learning his past from Vadivu, Maaran reconciles with Vetri and decide to finish Daniel, where they swap places. With Vetri (who is actually Maaran) seemingly in custody, Daniel meets him in prison and contemplates on misusing the medical industry for his personal gains. Meanwhile, Daniel's nephew Sesha tries to make a deal with Maaran (who is actually Vetri) to shut down his practice. However, when they both learn the truth, Vetri slits Sesha's hand. Daniel rushes to Vetri's hideout. Vetri defeats all of Daniel's henchmen and injures Daniel with a glass bottle, but just then, Kasi crashes a bus into Vetri, making him faint.

In the truck, Maaran also got involved in an accident orchestrated by Daniel, where he wakes Vetri up. As Vetri is injured, With Vetri's help, Maaran kills Kasi and also kills Daniel. Vetri is arrested for his role in the murders of all six people killed and is sentenced to life in prison. Before leaving, Vetri gives a press conference justifying his actions by exposing corrupt medical practices and embezzlement of money in the field; he adds that his endeavors will continue until the whole system is reformed. In prison, Vetri watches a news report in which, despite his efforts, another young girl in Odisha had died from negligent medical treatment.

On hearing this, Vetri escapes using his magic tricks and continues his mission. In the end, Maaran has conferred a statewide recognised medical counselor post.