Ramachandran is a geneticist who does not get due credit and funds for his research. He tries creating a human with several talents through baby designing, which leads to the birth of his sons, who are conjoined together above the waist. Since they share a common heart, doctors suggest a sacrificial surgery, to which their mother Sudha objects. They begin raising their children, Vimalan and Akilan. Vimalan and Akilan are poles apart in character, Vimalan being decent, intellectual, and good at studies; while Akhilan is happy-go-lucky, socializing, and poor at studies.

In the following years, Ramachandran makes it big with Sudha's help. His company, Locus Lacto Products, makes a huge profit through their product 'Energion', the top-selling children's powdered milk energy drink in the market. Both Vimalan and Akilan are smitten by Anjali, who joins their company as a translator. She, along with her Russian friend Volga, a journalist, spend their time with the brothers. Meanwhile, Anjali falls for Vimalan. Akilan is jealous yet feels happy for them. Volga is then revealed to be a spy who tries to steal Energion's trade secrets. She is exposed and sent out by Ramachandran. She then takes the brothers to their cattle farm under the pretext of an interview, where she takes pictures and collects a milk sample from their farm.

When Vimalan confronts Volga, she warns him that Energion is an adulterated food product and can lead to the death of thousands of children. She tells that an employ named Ajay Ratnam who joined their company was actually a spy, and because of his cheat work, he was murdered. She also exposes their father of killing their R&D department head, Raghu and setting the lab on fire, thereby destroying evidence. Consequently, she is murdered, but swallows a pen-drive containing pieces of evidence of the foul play before dying, and is thrown out of the building. Anjali acquires it from the person who performs Volga's autopsy. She hands the pen-drive over to Vimalan. Following this, Vimalan and Akilan are confronted by goons who try to get the pen-drive from him. Akilan is convinced that the attack was only meant for robbing them. During this fight, Vimalan suffers a huge blow on the head.

Vimalan is declared brain dead, and his heart is transplanted into Akilan. After the twins are separated through a surgery that results in Vimalan's total death, Akilan and Anjali are depressed. Anjali moves on and falls for Akilan. Sudha is warned that Energion is adulterated, and she confronts her husband, who asks the food safety department to raid their company. To her surprise, Energion is just declared safe and hygienic. Meanwhile, Akilan discovers that his father is behind Vimalan's and Volga's deaths by tracking his assistant Dinesh. He gets hold of the pen-drive that contains several photos, where ingredients used as cattle feed at their farm are declared as very unsafe to eat. The beginning of the scheme is traced back to the European republic of Ukraine.

Accompanied by Anjali, Akilan sets out to solve the mystery. They get her friend Ashok's help who is an official in the Indian Embassy in Ukraine, but he is killed by Dinesh, who followed them there. The photos are revealed to be athletes who were competing as Unified team under the Olympic flag in the 1992 Summer Olympics. The athletes were declared dead in a plane crash. The investigation leads them to the army medical research centre. The truth is then revealed that Energion was, in fact originally a steroid invented by Ramachandran to improve the performance of the athletes at the world games. Despite the country performing well, some athletes began suffering from similar health problems leading to their deaths, and that their death from a plane crash was faked to avoid national shame. They also learn that the adulterant in Energion could only be detected using an ionization enhancer. After being assaulted by a local mafia led by Dinesh, Akilan manages to kill him and takes the ingredients back to India.

Once they are in India, Ramachandran is exposed and is about to be arrested. Akilan requests his father to surrender but finds out that he and his brother are just a result of their father's failed experiment and that he and his brother are actually made up of several talented people's DNA. Ramachandran states that he used the whole society as his research lab through Energion. His leg is then crushed by a rock after being unsuccessful in killing his son. Akilan leaves his father to die at the hands of rats which chew on his flesh. Akilan is conferred national recognition for bravery. He later marries Anjali, and they become parents to twins.