A Single Gentleman returns to England, now wealthy, after forty years. He seeks his elder brother, having lost contact after they quarrelled over their love for the same woman. The elder brother, Trent, lives in a curiosity shop with his granddaughter Nell, and is helped by Kit.

Quilp lends Trent money, believing him to be secretly rich and able to return a profit. Quilp's bullying of his wife angers her mother and friends. Quilp sits up all night smoking, and makes his wife stay up with him; meanwhile, Trent plays cards.

Nell delivers her a message from her grandfather to Quilp. Quilp notes that in five years Nell will be old enough to be his second wife. Nell tells Mrs Quilp that she is worried about her grandfather going out every night. At his counting house at the wharf, Quilp is visited by Dick Swiveller, who borrows money in lieu of his expectations from his Aunt. Quilp wants Swiveller to work in the legal office of his associates, Sampson Brass and his sister Sally. Quilp sends Swiveller to follow Trent, and discovers that Trent is a gambler who has lost his own savings and Quilp's loans. To recoup his losses, Quilp puts the shop up for sale, and awaits Trent's departure to death or a madhouse.

A schoolmaster has helped the Single Gentleman in his quest for Trent, but now leaves for a new job. They will keep in touch. The Gentleman continues to search London. Trent and Nell flee the shop. They will hide from Quilp and the threat of separation by wandering at random and withholding their identities. The Gentleman arrives too late, but is happy to learn that Trent has a grandchild. He and Quilp seek them separately. Quilp clashes with Kit, who refuses to help him find Trent and Nell.

Trent and Nell befriend Codlin and Short, members of a travelling Punch and Judy show. They accompany the travellers to a pub, The Jolly Sandboys. Codlin and Short wonder if the old man is leading Nell astray. Another man, Jerry, arrives with his performing dogs. Codlin drunkenly enters Nell's bedroom insisting that he, not Short, is her friend. Frightened that the men know their secrets and want to send them back, Nell and Trent flee. Quilp's coach passes them.

Trent and Nell meet Mrs Jarley, who employs Nell to give presentations at her waxwork exhibition. The Gentleman now lodges in Sampson and Sally Brass's property but will not give his name. Swiveller befriends and helps the Brasses' persecuted servant, whom he names the Marchioness.

With information from Codlin, Short and Jerry, the Gentleman traces Trent and Nell to Mrs Jarley - overheard by Quilp's friends - and travels with Kit's mother to find them. Nell has a nightmare about Quilp, and wakes to find Trent walking towards Mrs Jarley's room, where she keeps her profits. Claiming to have dreamed about an old man committing theft, Nell insists they leave. Quilp, the Gentleman and Kit's mother arrive, but Trent and Nell have left. After his wife and Brass misinterpret his absence as death, Quilp goes to live at his counting house. Kit confronts Quilp for frightening his mother.

Nell faints, and Trent seeks help from a nearby school. The schoolmaster asks them to stay until Nell recovers. They move into an old chapter house, with an allowance to look after the building. At Quilp's instigation, Sampson Brass hides money in Kit's hat and has him arrested.

The Marchioness goes to inform Swiveller about Kit's situation, but Swiveller is ill. Nell cleans the church, ill but not wanting to rest because she thinks herself a burden. The recovering Swiveller sends the Marchioness to inform the Gentleman about the actions that Quilp and the Brasses took against Kit. The police come for Quilp, who flees. Quilp falls into the river and is drowned.

Swiveller, the Marchioness and the Gentleman celebrate Kit's release. Now knowing Trent and Nell's identities, the schoolmaster writes to the Gentleman, his friend. The Gentleman and Kit rush to find Trent and Nell but they arrive too late. Nell has just died. Trent is distraught.