The movie is set on the life of an unnamed protagonist who is called Gandu by most who address him in the movie (an Indian slang/swear word that would literally translate to 'of the ass', the English translation running in the subtitle translates it to the English 'Asshole'). Gandu is portrayed as a frustrated teenager whose state of mind is shown by intercuts of him rapping in Bengali (it is later revealed in the movie that the protagonist is a member of a rap band). Gandu's sister seemingly supports the family through the magnanimity of her 'lover' Dasbabu (an unvoiced character who appears frequently) Gandu's sister and Dasbabu are shown having graphic sex a number of times. Gandu himself is shown repeatedly sneaking into the room of the copulating couple to steal money from Dasbabu's wallet. Gandu seemingly has complex emotions regarding this stealing and takes care to hide from his sister.
Gandu is also apparently quite lonely. His choice of hairstyle (shaved nearly bald) and general proclivity to drugs and rap makes him an object of ridicule in front of most of his peers, who mock him as 'an Egglike Gandu'. His loneliness is dispelled when he literally bumps into Rickshaw, a cycle rickshaw driver, who slaps Gandu and then scares him off by a bizarre show of Kung Fu (it is later revealed that Rickshaw literally worships Bruce Lee and models himself on his idol) That night Gandu has a dream of himself and Rickshaw in a near naked embrace (this has led to the common perception that Gandu and Rickshaw share a homosexual relationship but the movie itself never shows this explicitly and it maybe a more symbolic element)
On one of his stealing missions, Gandu's sister sees him and hides him from Dasbabu and seemingly laughs in complicity. This causes Gandu great anguish and he curses in frustration. His sister then knocks on his door and slaps him angrily and walks away. She is naked.
Gandu urges Rickshaw to 'take him away' Rickshaw and Gandu then go off to consume 'Dhatura Seeds' which causes them both to go on a strange and extremely intense trip. When they come to their senses they find they have no money. In a meta narrativistic scene the director Q himself drives into the scene and Gandu is told by Rickshaw how Gandu is a character in a movie being shot by Q. Gandu cannot quite comprehend this.
Gandu comes back to Kolkata to find that he has won a lottery of Rs. 50,000 (less than 1000 dollars), then he gives his mother some of the money and goes on a crack binge with Rickshaw. Rickshaw then admonishes him for never having actually sleeping with a woman despite incessantly rapping about cunt and pussy and sex. Gandu then has a surrealistic and very explicit sex scene (the only colour part in the movie and the reason being this is the only colorful/worthwhile moment in his life) with an unnamed woman who constantly meows (symbolizing a 'pussy' i.e female's genital in slang term) at the end of coitus she whispers 'demo' to him. Gandu goes back to Rickshaw telling him how he will now record a demo of his rap and show it to ADF (Asian Dub Foundation) The movie closes with Gandu finally becoming successful.
The film is shot mostly in black and white stressing on the bleak existence of the protagonist. At the end of the movie, the film shifts to the color mode (the reason being his life shifts from the dull black and white phase to a adventurous colorful happy life).
