Sethupathy(Kamalhassan) is an honest and upright police officer. When he arrests four bigwigs Dharmaraj(Nagesh), Francis Anbarasu('Delhi' Ganesh), Nallasivam(Nasser) and Satyamoorthy(Jaishankar), they escape justice easily and return to take revenge. They kill him and poison his wife(Srividya). She escapes and gives birth to twins but the babies are separated. Raja(Kamalhassan) grows up as a mechanic while Appu(Kamalhassan), a dwarf, grows up in the circus. When Appu comes to know of his father's murder, he decides to avenge his death by killing the four murderers.

The basic story in Aboorva Sagodharargal is immediately recognizable as the union of two of the oldest and most popular of cliches in tamil cinema. Brothers are separated at birth and take revenge on the people who killed their father. But by making one of the brothers a midget and fashioning the screenplay with an eye on humour, Kamalhassan makes us forget the age-old story and instead, takes us on a rollicking ride with a movie that is in equal parts amazing, funny, touching and most of all, thoroughly entertaining.

This is the only movie I can remember where the revenge theme is tackled with such liberal doses of humor. Though Kamal's meetings with Gouthami offer lots of laughs, it is the dwarf's height disadvantage that 'Crazy' Mohan's pen extracts the maximum mileage out of. Comments like the power of the message contained in the two lines of Thirukkural, the extra-long word coming out of his mouth and the mode of justice to be dispensed to Jaishankar, all sparkle with wit. And with many of these dialogs uttered by Kamal himself, they do not sound like making fun of his condition either. Janakaraj and his ever-praising assistant raise the laughs as they investigate the murders. The assistant showering adulation on Janakaraj for his every move and Janakaraj reacting stoically to these creates a very funny and memorable comedy track

Kamal's plans to kill the villains are a nice mix of both intelligent and fun. They are designed to raise laughs without reducing the scenes to slapstick. The ways he disposes off 'Delhi' Ganesh and Jaishanker are especially ingenious. The screenplay also turns funnier from this point, with the innocent Raja being in all the wrong places at the wrong times to make himself the prime suspect in the murders committed by Appu. Having Kamal and Gouthami travel in the lorry with the first dead body(Kamal even takes the arrow out and sticks it back in accordance with a line in the song!) is very funny while having Kamal dance a 'puliyaattam' after a tiger has killed someone, is a stroke of brilliance.

Kamalhassan as Appu also manages to touch our hearts with his unfulfilled romance. His innocent joy when Rupini asks him to accompany her to the register office and the shock as the realisation dawns that he is going to be a witness to her wedding are brought out so so beautifully on his face. His reaction when his mother points to him as an example of a man Rupini shouldn't have married is another touching scene.

Kamalhassan amazes us with his performance as Appu. He has obviously gone through quite a bit of physical strain to make the character believable(computer graphics had not yet entered tamil cinema at that point) and the effects are there to see. Though not flawless, it is an incredible effort. His Sethupathy has an effect inspite of the little screen time while Raja is just a bystander. Gouthami and Rupini have little to do. Nagesh makes a truly detestable villain though a couple of dialogs bring out his natural humor and lessen the evil of his role.

Ilaiyaraja stands by Kamal's side as always with some catchy tunes. Raja Kaiya Vecha..., sung by Kamal himself, has some fun lyrics comparing a car to a woman. Unna Nenache... is soothingly sung by SPB and Pudhu Maappillaikku... is a fun song with a catchy tune. Annaathe... is one of the best 'duppanguthu' songs in tamil and Kamal's exuberance tempts us to dance along with him.