Mohun Biswas is born in rural Trinidad to parents of Indian origin. His birth was considered inauspicious as he is born "in the wrong way" and with an extra finger. A pandit prophesies that the newborn child "will be a lecher and a spendthrift. Possibly a liar as well", and that he will "eat up his mother and father". The pandit advises that the boy be kept "away from trees and water. Particularly water". A few years later, Mohun leads a neighbour's calf, which he is tending, to a stream. The boy, who has never seen water "in its natural form", becomes distracted and allows the calf to wander off. Mohun then hides in fear of punishment. His father, believing his son to be in the water, drowns in an attempt to save him, thus in part fulfilling the pandit's prophecy. This leads to the dissolution of the family. Mohun's sister is sent to live with a wealthy aunt and uncle, Tara and Ajodha. Mohun, his mother, and two older brothers go to live with other relatives.
The boy is withdrawn prematurely from school and apprenticed to a pandit, but is cast out on bad terms. Ajodha then puts him in the care of his alcoholic and abusive brother Bhandat, an arrangement which also ends badly. Finally, the young Mr Biswas decides to make his own fortune. He encounters a friend from his school days who helps him get into the business of sign-writing. While on the job, Mr Biswas attempts to romance a client's daughter but his advances are misinterpreted as a wedding proposal. He is drawn into a marriage which he does not have the nerve to stop and becomes a member of the Tulsi household.
Mr Biswas becomes very unhappy with his wife Shama and her overbearing family. The Tulsis (and the big decaying house where they live) represent the communal way of life which is traditional throughout Africa and Asia. Mr Biswas is offered a place in this cosmos, a subordinate place to be sure, but a place that is guaranteed and from which advancement is possible. But Mr Biswas wants more. He is, by instinct, a modern man. He wants to be the author of his own life. That is an aspiration with which Tulsis cannot deal, and their decaying world conspires to drag him down. Despite his poor education, Mr Biswas becomes a journalist, has four children with Shama, and attempts several times to build a house that he can call his own, a house which will symbolize his independence.