E.M. Forster's A Passage to India concerns the relations between the English and the native population of India during the colonial period in which Britain ruled India. The novel takes place primarily in Chandrapore, a city along the Ganges River notable only for the nearby Marabar caves. The main character of the novel is Dr. Aziz, a Moslem doctor in Chandrapore and widower. After he is summoned to the Civil Surgeon's home only to be promptly ignored, Aziz visits a local Islamic temple where he meets Mrs. Moore, an elderly British woman visiting her son, Mr. Heaslop, who is the City Magistrate. Although Aziz reprimands her for not taking her shoes off in the temple before realizing she has in fact observed this rule, the two soon find that they have much in common and he escorts her back to the club.
Back at the club, Mrs. Moore meets her companion, Adela Quested, who will likely marry her son. Adela complains that they have seen nothing of India, but rather English customs replicated abroad. Although a few persons make racist statements about Indians, Mr. Turton, the Collector, proposes having a Bridge Party (to bridge the gulf between east and west). When Mrs. Moore tells her son, Ronny, about Aziz, he reprimands her for associating with an Indian. When Mr. Turton issues the invitations to the Bridge Party, the invitees suspect that this is a political move, for the Collector would not behave so cordially without a motive, but accept the invitations despite the suspicion.
For Adela and Mrs. Moore, the Bridge Party is a failure, for only a select few of the English guests behave well toward the Indians. Among these is Mr. Fielding, the schoolmaster at the Government College, who suggests that Adela meet Aziz. Mrs. Moore scolds her son for being impolite to the Indians, but Ronny Heaslop feels that he is not in India to be kind, for there are more important things to do; this offends her sense of Christian charity.
Aziz accepts Fielding's invitation to tea with Adela, Mrs. Moore, and Professor Narayan Godbole. During tea they discuss the Marabar Caves, while Fielding takes Mrs. Moore to see the college. Ronny arrives to find Adela alone with Aziz and Godbole, and later chastises Fielding for leaving an Englishwoman alone with two Indians. However, he reminds Ronny that Adela is capable of making her own decisions. Aziz plans a picnic at the Marabar Caves for Miss Quested and Mrs. Moore. Adela tells Ronny that she will not marry him, but he nevertheless suggests that they take a car trip to see Chandrapore. The Nawab Bahadur, an important local figure, agrees to take them. During the trip, the car swerves into a tree and Miss Derek, an Englishwoman passing by at the time, agrees to take them back to town. However, she snubs the Nawab Bahadur and his chauffeur. Adela speaks to Ronny, and tells him that she was foolish to say that they should not be married.
Both Aziz and Godbole fall sick after the party at Mr. Fielding's home, so Fielding visits Aziz and they discuss the state of politics in India. Aziz shows Fielding a picture of his wife, a significant event considering his Islamic background and an important demonstration of their friendship.
Aziz plans the expedition to the Marabar Caves, considering every minute detail because he does not wish to offend the English ladies. During the day when they are to embark. Mohammed Latif, a friend of Aziz, bribes Adela's servant, Antony, not to go on the expedition, for he serves as a spy for Ronny Heaslop. Although Aziz, Adela and Mrs. Moore arrive to the train station on time, Fielding and Godbole miss the train because of Godbole's morning prayers. Adela and Aziz discuss her marriage, and she fears she will become a narrow-minded Anglo-Indian such as the other wives of British officials. When they reach the caves, a distinct echo in one of them frightens Mrs. Moore, who decides she must leave immediately. The echo terrifies her, for it gives her the sense that the universe is chaotic and has no order.
Aziz and Adela continue to explore the caves, and Adela realizes that she does not love Ronny. However, she does not think that this is reason enough to break off her engagement. Adela leaves Aziz, who goes into a cave to smoke, but when he exits he finds their guide alone and asleep. Aziz searches for Adela, but only finds her broken field glasses. Finally he finds Fielding, who arrived at the cave in Miss Derek's care, but he does not know where Adela is. When the group returns to Chandrapore, Aziz is arrested for assaulting Adela.
Fielding speaks to the Collector about the charge, and claims that Adela is mad and Aziz must be innocent. The Collector feels that this is inevitable, for disaster always occurs when the English and Indians interact socially. Fielding requests that he see Adela, but McBryde, the police superintendent, denies this request. Fielding acts as Aziz's advocate, explaining such things as why Aziz would have the field glasses. Aziz hires as his lawyer Armitrao, a Hindu who is notoriously anti-British. Godbole leaves Chandrapore to start a high school in Central India.
The Anglo-Indians rally to Miss Quested's defense and call a meeting to discuss the trial. Fielding attends, and makes the mistake of actually referring to her by name. The Collector advises all to behave cautiously. When Ronny enters, Fielding does not stand as a sign of respect. Mr. Turton demands an apology, but Fielding merely resigns from the club and claims he will resign from his post if Aziz is found guilty.
Adela remains in the McBryde's bungalow, where the men are too respectful and the women too sympathetic. She wishes to see Mrs. Moore, who kept away. Ronny tells her that Fielding wrote her a letter to her pleading Aziz's case. Adela admits to Ronny that she has made a mistake and that Aziz is innocent. When Adela sees Mrs. Moore, she is morose and detached. She knows that Aziz is innocent and tells Adela that directly. Mrs. Moore wishes to leave India, and Ronny agrees, for she is doing no one any good by remaining. Lady Mellanby, the wife of the Lieutenant-Governor, secures Mrs. Moore quick passage out of India.
During the trial, the Indians in the crowd jeer Adela for her appearance, and Mahmoud Ali, one of Aziz's lawyers, claims that Mrs. Moore was sent away because she would clear Aziz's name. When McBryde asks Adela whether Aziz followed her, she admits that she made a mistake. Major Callendar attempts to stop the proceedings on medical grounds, but Mr. Das, the judge, releases Aziz. After the trial, Adela leaves the courtroom alone as a riot foments. Fielding finds her and escorts her to the college where she will be safe. Disaster is averted only when Dr. Panna Lal, who was to testify for the prosecution, publicly apologizes to Aziz and secures the release of Nureddin, a prisoner rumored to have been tortured by the English.
At the college, Fielding asks Adela why she would make her charge, but she cannot give a definite answer. He suggests that she was either assaulted by the guide or had a hallucination. Adela seems to believe that she had a hallucination, for she thinks she had a hallucination of a marriage proposal when there was none. Fielding warns her that Aziz is very bitter. Ronny arrives and tells them that his mother died at sea.
After a victory banquet for Aziz, he and Fielding discuss his future plans. Fielding implores Aziz not to sue Adela, for it will show him to be a gentleman, but Aziz claims that he is fully anti-British now. Fielding reminds Aziz what a momentous sacrifice Adela made, for now she does not have the support nor friendship of the other English officials. Fielding tells Aziz that Mrs. Moore is dead, but he does not believe him. The death of Mrs. Moore leads to suspicion that Ronny had her killed for trying to defend Aziz. Although there was no wrongdoing in the situation, Ronny nevertheless feels guilty for treating his mother so poorly. Adela decides to leave India and not marry Ronny.
Fielding gains new respect for Adela for her humility and loyalty as he attempts to persuade Aziz not to take action against Adela. Adela leaves India and vows to visit Mrs. Moore's other children (and Ronny's step-siblings) Stella and Ralph. Aziz hears rumors and begins to suspect that Fielding had an affair with Adela. He believes these rumors out of his cynicism concerning human nature. Because of this suspicion, the friendship between Aziz and Fielding begins to cool, even after Fielding denies the affair to Aziz. Fielding himself leaves Chandrapore to travel, while Aziz remains convinced that Fielding will marry Adela Quested.
Forster resumes the novel some time later in the town of Mau, where Godbole now works. Godbole currently takes part in a Hindu birthing ceremony with Aziz, who now works in this region. Fielding visits Mau; he has married, and Aziz assumes that his bride is Miss Quested. Aziz stopped corresponding with Fielding when he received a letter which stated that Fielding married someone Aziz knows. However, he did not marry Adela, as Aziz assumes, but rather Mrs. Moore's daughter, Stella. When Fielding meets with Aziz and clears up this misunderstanding, Aziz remains angry, for he has assumed for such a long time that Fielding married his enemy.
Nevertheless, Aziz goes to the guest house where Fielding stays and finds Ralph Moore there. His anger at Fielding cools when Ralph invokes the memory of Mrs. Moore, and Aziz even takes Ralph boating on the river so that they can observe the local Hindu ceremonies. Their boat, however, crashes into one carrying Fielding and Stella. After this comical event, the ill will between Aziz and Fielding fully dissipates. However, they realize that because of their different cultures they cannot remain friends and part from one another cordially.