The novel opens with young unemployed Martin, heir to his very rich
grandfather Martin Chuzzlewit Senior, leaving safe and
secured home turf to eke out a living so that he can marry and support his childhood love Mary Graham. His
grandfather seems to have become misanthropic due to the greed of his many relatives. The wise old man is looked after by Mary Graham, an orphan, who he has brought up for that purpose, who he sees as his daughter and nurses a secret desire to marry her to his only grandchild young Martin. When our hero vows his love to Mary without asking for the grandfather's consent then grandfather thinks his
grandson must first become his own man and understand importance of money earned through hard labour. Moreover old man is suspicious of his grandson’s self-concerned nature and doesn’t want his heir to squander money on useless pursuit and more than his grandson he wants Mary to be happy post marriage. So he dismisses Martin from his inheritance.
Martin is given an internship by hypocritical architect Mr. Pecksnif. Pecksnif is a distant relative of senior Martin and has an eye for old man’s wealth. By employing Martin he tries to kill two birds with one stone. First Pecksniff wants one of his two daughters to marry our hero and secure part of old man’s inheritance as Martin senior is not in good health and may die without writing a will. If that fails then he wants to be in good books of both grandfather and grandson esp. grandfather’s and secure the inheritance for himself.
Young Martin quickly sees through Pecksniff and decides to go to America to seek his fortune, accompanied by his friend and servant, Mark Tapley. In America he is ill treated by elite of society for being poor and is coaxed into buying swampland by a fraudulent company. While working hard to make both ends meet he falls seriously ill and selfless, cheerful Tapley nurses him back to health. This experience makes him a positive and decent man of impeccable character. He and Mark then decide to return to England but they don’t even have enough money to finance their trip back home. Tapley takes up the job of errands man in a ship sailing to Britain in lieu of boarding and lodging. Penniless Martin follows suit and is greatful to God for it.
While he is gone the evil Mr. Pecksniff seems to gain some influence over the grandfather. He also begins to make love to Mary and tries to persuade her to marry him, as he believes old man will relinquish his wealth to Mary. Briefly the story also focuses on senior Martin’s greedy brother and his evil son, Jonas. Jonas Chuzzlewit marries one of Pecksniff’s daughters for her dowry and tortures her for money. Jonas plots his father’s murder, runs a fraudulent company to dupe people of their savings and later meets a tragic end like his father.
After reaching England Martin hopes to reconcile with his grandfather and is ready to do any menial job to earn his living. At first Martin is unsuccessful but when the grandfather has made certain of young Martin’s reinvention as a good individual, he ensues resolution and brings his grandson back into favor. Martin senior also reveals that he had not really been under Pecksniff's influence, that he had known Pecksniff's evil character from the start, and that he had only wished to test how far he would go. The grandfather and Martin are reconciled and Martin's marriage to Mary is approved.