He Knew He Was Right is an 1869 novel written by Anthony Trollope which describes the failure of a marriage caused by the unreasonable jealousy of a husband exacerbated by the stubbornness of a willful wife.

Meanwhile, Nora attracts two admirers, the wealthy Charles Glascock, the eldest son and heir of Lord Peterborough, and Hugh Stanbury, a close friend of Trevelyan's from their days at Oxford University.

Glascock proposes to Nora, but despite the fact that Stanbury has given no indication of his feelings for her, she rejects the future nobleman, not without a great deal of struggle and much to the dismay of her friends.

Aware of the poverty of Hugh's branch of the family, she had generously paid for his education and helped him get a start in life.

In the meantime, Aunt Stanbury tries to promote a marriage between her niece Dorothy and a favoured clergyman, Mr Gibson.

This causes much resentment with Arabella and Camilla French, two sisters who had considered him a future husband for one of them (though which was still a matter of much debate).

Finally, finding Camilla's overpowering personality unbearable, he extricates himself by agreeing to marry the milder Arabella instead.

Camilla is driven to extravagant threats and is finally sent to stay with her stern uncle in the period leading up to the wedding.

Then Aunt Stanbury becomes very ill, resulting in Dorothy and Brooke spending a good deal of time in each other's company.

Glascock's father is in such poor health that the son is obliged to remain in the country to await his probable demise.

While Osborne had not been permitted to see Emily, Trevelyan does not believe it and has the boy taken away from his mother by deception; he takes his son back to Italy, where he descends further into madness.

Louis Trevelyan's single-minded belief in his wife's adultery (as implied by the title) leads to his downfall, while Miss Jemima Stanbury is similarly obsessed with her money and social status.

Bozzle's determination to prove Emily Trevelyan's unfaithfulness is similarly portrayed as obsessive, gradually breaking the rules of good taste and compassion as his investigations continue.

The book's title makes this theme explicit; the characters who 'Know They Are Right' display stubbornness, obsession and a manic pursuit of their goals that leads to madness.