Nachiappan, Nassar is a widowed, wealthy, and successful Indian American restaurateur based in Los Angeles. He has two sons – Viswanathan "Visu" and Ramamoorthy "Ramu" – who are identical twins. They both are medical students and spend their evenings helping out their father alongside the restaurant's chief cook, Juno. One evening, when Visu and Ramu head to the airport to restock the kitchen, Visu spots a Tamil family from Chennai — Madhumitha "Madhu", her younger brother Madhesh, and their grandmother Krishnaveni — facing trouble with immigration authorities. Visu steps in to help, learning that they’ve just flown in from India so that Krishnaveni can undergo brain surgery. After a sequence of misunderstandings, the trio meets with Ramu, and the twins arrange for the family to reach their host.
Krishnaveni is admitted to the hospital where Visu works as a resident doctor, and the surgery is performed. Visu quickly realises that Krishnaveni has been paralyzed because the operation was done on the wrong side of her brain due to a mix-up with another patient. He raises a fierce, principled challenge to the doctors and helps obtain a corrective surgery, then leads a high-profile fight for compensation. The hospital agrees to pay US$2 million to avoid a court case. This sequence brings Madhu and Visu closer, and Madhu begins to fall in love with him.
Krishnaveni decides to prolong the family’s stay in the US to sort things out, but Nachiappan objects to the romance because he hopes his sons will marry identical twin girls. A flashback reveals a bitter chapter from Nachiappan’s past: he had a conjoint twin brother, Pechiappan, who lived in Karaikudi and was a simple man. In their youth, they both married for love, but Pechiappan’s wife Sundaramba tortured Nachiappan’s pregnant wife Meiyaththa so badly that she died after giving birth to Visu and Ramu. Nachiappan ultimately left with his sons to shield them from further harm and to keep Pechiappan and Sundaramba from harming the family.
Krishnaveni’s plan to resolve the situation involves a bold lie: she tells Nachiappan that Madhu has an identical twin named Vaishnavi, raised separately in a conservative Brahmin household, because she believes twins would bring luck to their family. The group travels to India to “meet” Vaishnavi and arrange the marriages of Visu to Madhu and Ramu to Vaishnavi. Madhu herself agrees to impersonate Vaishnavi, a demure and traditional persona, while Visu remains unaware that Vaishnavi does not actually exist. Ramu falls for Vaishnavi, not realizing she is Madhu.
Meanwhile, Pechiappan’s own marriage with Sundaramba has deteriorated, and he even attempts suicide. Nachiappan rescues him and hatches a plan to bring the two families together through the arranged marriages. Pechiappan impersonates Nachiappan, and Nachiappan returns the favor by impersonating Pechiappan, venturing to Karaikudi to salvage his brother’s struggling restaurant business. In a parallel turn, Pechiappan steps into Nachiappan’s life and stays with Visu and Ramu, assisting with the family’s complexities.
As the story unfolds, Madhu discovers that Ramu is deeply in love with her Vaishnavi alter ego, and she realises she has been hurting both brothers by continuing the ruse. Visu also uncovers that Vaishnavi does not truly exist. Ramu encourages his father to reconcile Visu and Madhu, and Nachiappan learns the truth about the impersonations. He rushes to Chennai with Sundarambal, intending to stop the wedding, but Sundarambal persuades him to let the couple wed, arguing that Madhu, in her Vaishnavi role, helped reunite the families in the same way Nachiappan and Pechiappan had attempted. The couple, Viswanathan and Madhumitha, finally marry, and Madhesh adds a light finale with computer-generated effects, celebrating the union and the families’ reconciliation.
