His long-estranged wealthy older brother, recently retired to England after a career spent abroad, is drawn into covering up Austin's misdeeds and accidents.

A second plot line involves Ludwig Leferrier, a young American academic who has resolved to stay in England in order to avoid the draft, but struggles with his decision throughout the book.

Austin blames his brother for having injured him when they were children, leaving him with a deformed right hand, and for having had an affair with his first wife, both of which accusations Matthew denies.

The novel begins with the engagement of Ludwig Leferrier, a young American historian, to Gracie, the daughter of George and Clara Tisbourne.

During the course of the novel Ludwig begins to question his relationship with Gracie, who does not share his intellectual and moral seriousness, and who discourages him from trying to help Dorina and Charlotte.

Other important characters include Austin's son Garth, who had been Ludwig's friend as a student at Harvard, and who also returns to London at the outset of the novel; Dorina's sister (and Matthew's lover) Mavis, a social worker who has lost her religious faith; and Mitzi Ricardo, a former star athlete whose career was ended by a freak accident and who works as a typist.

Both Mitzi and Charlotte attempt suicide by taking overdoses of sleeping pills, but both are rescued in time and are taken to recover in the same hospital ward.

Austin's wife Dorina, having left Mavis's house where she had been staying, goes into hiding in a hotel, where she dies accidentally when an electric heater falls into her bathtub.

Ludwig is tormented throughout the novel by his decision to marry Gracie and stay in England, while his parents plead with him to return to the United States.

The accidental death of Dorina just after he has passed her in the street without acknowledgement awakens him to his complicity with Gracie's uncharitable attitudes and leads to the discussions with Matthew which result in Ludwig's going home.

[2]: 166–167  However, Austin's chronic bad luck, which appears to be "an infectious moral flaw", calls into question the universality of the Good Samaritan's message of helping the unlucky.

[7] In The New York Times Anatole Broyard wrote that with An Accidental Man Iris Murdoch had "become, at last, a complete novelist", in that she had succeeded in making her characters believable.

[9] Nora Sayre, in The New York Times Book Review, remarked on the individuality of the characters and their inability to "help or simply influence one another", noting the absence of "all-powerful sorcerers".

[5]: 81–82  Angela Hague describes the novel as a "brittle comedy of manners" and says that Murdoch's purpose was to create a "Dickensian sweep of characters".