Kunjunni Menon, Santhosh Keezhattoor, a witty thief, falls in love with Lakshmi Lenaa Nair, a police constable. While tailing her one day, he discovers that she wishes to marry a policeman. Vasudeva Shenoy, Anoop Menon, Lakshmi's colleague, expresses his desire to marry her despite his mother's objections. Kunjunni poses as a police constable and marries Lakshmi before Shenoy can convince his mother. Shenoy gets married, and both couples are blessed with baby boys on the same day. Lakshmi finds out that Kunjunni cheated her, but they pretend to have an amicable marriage.
A young Adhithyan, Dulquer Salmaan, still believes his father to be a policeman, and he and Vikram Shenoy, Unni Mukundan Shenoy's son, become rivals in school, wagering that the loser should salute the winner, a habit they carry into adulthood. Adhithyan always ends up losing.
One day, Kunjunni is caught red-handed by Shenoy and his team while attempting a robbery and is paraded half-naked throughout the street. Unable to face a distraught Adhithyan and berated by Lakshmi, Kunjunni reaches a bridge and commits suicide. Years later, Vikram becomes a hardworking young man while Adhithyan becomes lazy and indulges in petty illegal activities to earn money. Adhithyan falls in love with Deepika, Vikram's close friend Namitha Pramod.
Once the duo pass their degrees, they both decide to apply for the SI selection test. Though the two share a healthy rivalry, Shenoy is spiteful toward Adhithyan, who outranks Vikram in the preliminary round. However, Vikram acknowledges Adhithyan's superior intellect, displaying his deep respect for his rival. Shenoy traps Adhithyan in a narcotics case and is desperate to put him behind bars. He also guards the evidence personally. Adhithyan is saved when Vikram secretly swaps the evidence with lactose powder. Adhithyan expresses his gratitude, revealing that the respect they hold is mutual.
In a final attempt, Shenoy convinces Lakshmi that he is the one who swapped the evidence and asks her for a favor in return. Lakshmi hides the interview memo Adhithyan was to receive and only Vikram's name appears on the list for the final exam. A heartbroken Adhithyan blames Lakshmi for Kunjunni's death and claims that she could have changed him had she tried. Adhithyan disappears that night.
Two years later, Vikram becomes the new SI and takes charge on Shenoy's retirement. The new sub-collector Lokesh arrives to congratulate the father and son. Lokesh reveals that he met Adhithyan on a train journey to Delhi and stopped him from committing suicide. The two later become close friends and roommates. On Lokesh's insistence, Adhithyan prepares for the UPSC exams while doing odd jobs in between. Both pass the exam together, and Lokesh reveals that Adhithyan is now an IPS officer in the Kerala cadre and has been posted as ACP, Shenoy and Vikram's superior. Shenoy is forced to accept defeat and salutes Adhithyan. Satisfied with his revenge, Adhithyan decides not to tell Vikram. Vikram eventually learns the truth and salutes Adhithyan publicly, and the two embrace, acknowledging their friendship as Vikram asks Adhithyan to accept Deepika's love and reveals that his next goal will be to catch up with Adhithyan.
