Three English art students in Paris (Taffy, Laird, and William Bagot alias 'Little Billee') meet musicians Svengali and Gecko and the artist's model and laundress Trilby O'Ferrall.Trilby is cheerful, kindhearted, bohemian, and completely tone-deaf: "Svengali would test her ear, as he called it, and strike the C in the middle and then the F just above, and ask which was higher; and she would declare they were both exactly the same." To the bemusement of the other characters, Trilby is unable to sing "Ben Bolt" in tune. Yet despite being off-key, her singing voice nonetheless has an impressive quality.The Englishmen and Trilby become friends. Svengali tries to persuade Trilby to let him train her voice, but she finds him repulsive and even frightening. She and Little Billee fall in love, but his scandalized relatives get her to promise to leave him. She leaves Paris with her little brother, who later dies of scarlet fever. Trilby then falls under Svengali's influence. He hypnotises her and transforms her into a diva, La Svengali. Under his spell, Trilby becomes a talented singer, performing always in an amnesiac trance.Five years later, Little Billee is a famous painter. He, Laird and Taffy recognise Trilby as she performs at a concert. Trilby sings beautifully but does not appear to be in good health.Shortly before another performance, Gecko suddenly turns on Svengali and slashes him with a penknife. At the concert, Svengali is stricken by a heart attack and is unable to induce the trance. Trilby is unable to sing in tune and is subjected to "laughter, hoots, hisses, cat-calls, cock-crows." Not having been hypnotised, she is baffled and, though she can remember living and travelling with Svengali, cannot remember anything of her singing career. Suddenly an audience member yells: "Oh, ye're Henglish, har yer? Why don't yer sing as yer ought to sing - yer've got voice enough, any'ow! Why don't yer sing in tune?" she cries "I didn't want to sing at all - I only sang because I was asked to sing - that gentleman asked - that French gentleman with the white waistcoat! I won't sing another note!"As she leaves the stage, Svengali dies. Trilby is stricken with a nervous affliction. Despite the efforts of her friends, she dies some weeks later-staring at a picture of Svengali. Little Billee is devastated and dies shortly afterwards.Some years later, Taffy meets Gecko again and learns how Svengali had hypnotised Trilby and damaged her health in the process. Gecko reveals that he had tried to kill Svengali because he could not bear to see Trilby hurt during their awful rehearsals