The film begins with the song "manju mazhakattil" showing the family of young Gautham Menon moving into Srinagar and their getting used to the Kashmir life. Later a group of terrorists besiege the village and kill Gautham’s parents. Gautham’s older sister pulls him away from the killers and hides behind woods. A terrorist finds them and a gunshot is heard. Later his sister is seen to be in the Hospital in critical stage and the Doctor asks him to pray for her. The song continues and Gautham is shown growing to a teenager and winning accolades from school. He runs to the hospital to share the joy with his still hospitalized sister, but sees her dying in the hospital bed.
The story turns to the present where an adult Gautham Menon (Dileep) goes to see the old doctor uncle Babu Namboothiri who was a friend of his late father and his mentor during his childhood. Gautham says his company posted him to India and he can choose his posting between Chennai and Bangalore.
He goes to see an old Army officer, Major George Joseph (Lal (actor)), who was discharged from his duties for having squabbles with superiors while drunk. He tells Gautham that he had his family killed in an accident resulted from his drunk driving. Gautham reveals himself to Major as the kid from the past who was compassionately consoled by him after the military operation that killed the terrorists that attacked Gautham’s village.
Meanwhile a journalist comes to visit Rtd. General Hareendranath Varma (Satyaraj) to publish his biography. The General reluctantly accepts the offer. Later he sees his mother trying to call Shreya, daughter of Varma, asking her to stop by while en route to Bangalore, that they could proceed her marriage with an NRI boy. Knowing the intentions of Grandma, Shreya (Charmee Kaur) dodges the calls saying she can hardly hear her while travelling on the bus. The bus hits an old woman. Gautham, sitting next to Shreya, carries the women to bus demanding to take her to hospital. He asks the help of Shreya to carry her to the hospital. The driver takes the bus leaving behind Gautham and Shreya at the hospital. Later the relatives of the victim come to hospital and takes money from Gautham as compensation. Gautham and Shreya leave and have to wait till 10 PM to catch the next Bus to Bangalore, where Shreya has to pay all the expenses.
Shreya finds Gautham gone in the morning, but after repaying her the expenses and a note left behind. She is picked up by her cousin and cousin's husband (Biju Menon). Incidentally Gautham also rents the house owned by Biju Menon’s brother and befriends his family, though he tactfully dodges Shreya every time she sees him. Shreya develops a fondness towards Gautham, despite not knowing anything about him including his name. Meanwhile her Grandma arrives to Bangalore and Biju Menon comes up with the proposal of Gautham for Shreya. Grandma likes Gautham upon seeing him. But Shreya, already in love with ‘stranger’, does not agree to it. Later ‘stranger’ reveals himself to Shreya as Gautham. Varma invites Gautham to his farmhouse to meet him. Gautham wins everybody’s heart with his polite and gentle manner. Later he beats the General in a chess game and gains his admiration. That moment Gautham reveals himself as a survivor of the terrorist attack foiled by Varma’s army which upsets the general.
Gautham speaks to the General in Private and reveals the truth that his sister was cruelly raped by the then commanding officer Varma after killing all the terrorists knocking her unconscious for the rest of her life. Varma asks Major George, who was a silent witness to his cruelty, to report it as a terrorist act thereby hiding the truth. Gautham swears to the General that he will make him reveal the truth to everyone.
Gautham gets close to everyone in the family which annoys Varma who tries everything to get rid of him. Gautham proves to Varma that Shreya is madly in love with him. Varma takes Gautham out for a ride and threatens to kill him by pointing a gun, but Gautham has already texted Shreya to follow them, thereby foiling Varma’s attempt. Later Varma almost succeed in killing Gautham by locking him in the wine preserving barrel, but Gautham escapes with the help of Lawrence (Innocent (actor)), Varma's servant. He challenges Varma that he will make him reveal the secret in two days, that is at the engagement ceremony.
A large party of the General's ex-colleagues, including Major George, is invited to the function by Gautham using Varma’s email id. It is also revealed that the journalist chronicling Varma’s biography has also been sent by Gautham to trap him. The media people are also invited. All these were done so that when the secret is revealed, all will come to know easily.
At the function, Varma presents himself in the Army General’s uniform. He reveals the secret to all the invited guests in the guise of a dirty plan by Gautham to blackmail him. Varma also says that if anyone among the guests believes the story, he will shoot himself. But all keep quiet. Gautham challenges General to shoot him if the story is a scam. Though the General points the gun towards Gautham, he cannot pull himself to shoot him, thereby silently admitting the crime. Soon all the guests turn against him. Realizing his mistake and out of guilt, he leaves the scene and kills himself after writing down the confession to the President of India and returning all the accolades and awards he received during his service.
The film ends with Shreya sitting in an airport receiving a letter passed on to her. She reads it to find it from Gautham asking if she still has feelings for him. She sees him sitting a bit far away smiling at her.Dileep as Goutham Menon
Sathyaraj as Gen. Hareendranath Varma
Charmee Kaur as Shreya
Lal as Maj. George Joseph
Biju Menon as Dr.Sudhir Krishna
Innocent as Lawrence
Zarina Wahab as Malathi Varma
Valsala Menon as Shreya's Grandmother
Shafna as Gautham's Sister
Anand as Gautham's father
Archana Menon as Gautham's mother
Majeed as Rakhi's and Deepthi's father
Ambika Mohan as Rakhi's and Deepthi's mother
Shilpa Bala as Deepthi
Reena Basheer as Rakhi
Dileep signed into play the male lead while Tamil actor Sathyaraj signed into play the antagonist marking his Malayalam debut.
Vidya Balan was considered to play the female lead even though she was interested in the character couldn't take up due to prior commitments.Later Mamta Mohandas signed into play the role but opted out citing health issues.Finally Telugu actress Charmee Kaur replaced the later marking her come back to Malayalam industry after a hiatus of 8 years.
The film received mixed reviews from both critics and audience. Veeyen of Nowrunning.com commented "Aagathan has an 'I know what's round the corner' quality all over it despite a stunning backdrop and an unusually subtle soundtrack. It's a psychodrama gone wrong, precisely because the denouement that it hopes to cash on is a bit too obvious, and comes at the wrong instant". The film was acclaimed well by the audience by the choreography done in the film.
The film had a hard competition with Chattambinadu, Ividam Swargamanu, Happy Husbands, Drona 2010 and Dileep's other film Bodyguard. The film was declared average success at box office.
The film's soundtrack, composed by Ouseppachan and lyrics penned by Kaithapram, was met with positive reviews. Shreya Ghoshal, who performed one of the tracks, won the Best Female Playback Singer Award at the 13th Asianet Film Awards. She also won the Kerala Film Critics Award for Best Female Playback Singer.Track listing