The story of Hepaah revolves round the rise of a ragtag band of five young small-town musicians against the backdrop of "politically turbulent" Assam. The five musicians plan to launch their band at a concert. A middle-aged man, Kakati (Biju Phukan), who owns a furniture shop, comes to help them out. With his help and patronage, the boys hold successful shows and eventually Kakati becomes the mentor of the band and named it "Hepaah".
The band succeeds to gain popularity and accolades among masses. But before things can take concrete shape, there comes a rich man, with the proposal of producing an audio album of them. The huge commercial success of the album brings money and means to the group, alleviating their day-to-day hardship.
They begin to lose their commitment to music. Kakati, disillusioned by their attitude, decides to leave them to their fate. But before everything goes out of control, the troupe members make a last effort to hold on to their ideals. But it is already too late. Nothing materializes in the end, only their aspirations, desires remained unfulfilled.