Officer Muthukumar fights against a dreaded don Gurumurthy, but soon he gets embroiled in a brawl with the corrupt system, following the death of Gurumurthy.

Outgoing Meera (Rekha) and shy Nithya (Kaveri) are best friends since childhood. They share an apartment together in an expansive complex. One day, handsome Venkat (Nanda) moves in with his grandparents, and Meera is smitten She starts to make anonymous calls to him, and he finds himself falling in love with her. A friend suggests that he use caller ID to locate her, which he does. At that time, Meera hands the phone to Nithya to run an errand. Nithya is the face he sees holding the phone, and despite being engaged to Shakti, she likes him too…..

A youngster sets out in search of a treasure based on the clues left behind by his grandfather.

Madhiazhagan (Nandha) is a highly successful project manager at a leading property promoters firm. He’s happily wedded to Vasugi (Ananya) and has a five-year-old daughter Pavi. Posh house, heftily paying job, highly appreciative and supportive boss, and a happy family – Madhi’s life is a far fetched dream to most people in this era. But all changes one day, when a man requests to be dropped en route, when Madhi and Vasu set out on a pleasant weekend. The mysterious stranger pulls out a pistol and begins to threaten the couple to bend to his wishes, holding Pavi as hostage. And the day sets off with the stranger making the couple draw out all the money Madhi has, to the last penny and setting it all on fire. Next, he makes Madhi lose his career by leaking the top secrets of his company, trusted to him, to their competitor. And the day goes on with further more gimmicks by the stranger, while the couple are cornered to do it all for their little daughter’s life. And for the same reason, they also refrain from making a complaint to the police, although they are tantalizingly near their target. While this seems endless, how they figure a way out of the mess, with a completely unexpected twist to the whole story in the end, ‘Athithi’ is an edge-of-the-seat realistic thriller.

The film opens to a school in a village where a boy recites a national anthem before all the staff and students of the school. Another boy is seen running to school as he is late. His teacher punishes him, while comparing him to the boy who recited earlier, who is revealed to be his younger half-brother. An enmity grows in the older brother as he is always compared to his younger brother. The younger brother burns the photo of the older brother’s father as he was the reason for his defeat in the school’s kabbadi match. In retaliation, the older brother throws the younger brother into a well. Watching him get drowned in the well, the older brother runs away from the village.

The local party leader gets hospitalized, Dr. Gayathri tries her best to cure him, but he dies. The leader’s son is forced to take over while Dr. Gayathri tells him about the conspiracy over his father’s death.

Ariyaan deals about two youthful lovers whose love life gets into many struggles. A ad film maker is in love with college student and their love meets with various turn and twist. This forms the rest of the story.

Nandha (Nandha Durairaj) is an upright sub-inspector of police who has been transferred 15 times in three years. He is then transferred in a police station based in Pollachi. There, Police Inspector Pandian (Natarajan Subramaniam) is in the pay of Minister Periyannan (Rajagopalan), who runs in own government in the place. Nandha is shocked to note that Pandian and the entire police department are corrupt. Thereafter, Nandha tries hard to enforce the order. Soon, both policemen clash. Pandian becomes an honest policeman after Periyannan’s men attempt to kill him, and he is revived with blood transfusions from the public. However, Nandha does not believe that he has truly changed. After a fellow honest sub-inspector gets killed by Periyannan’s men, Nandha blames Pandian, and through short routes, becomes inspector himself. He arranges for Periyannan and his men to clash with Pandian, but in the ensuing fight, Pandian kills them all, while Nandha walks away.

A Misogynist’s attitude towards women and love starts to change after he develops feelings for a woman.

Arjun was ordered by her girl friend that she would marry him only if he convinces a suave don to surrender to police.

A spoiled young heiress marries a poor man in order to inherit her grandfather’s property.

Vasu finds the dead body of Ramya in an apartment and decides to find her murderer. During the investigation, Vasu encounters more killings and learns that Ramya’s spirit is behind their death.