Fingersmith follows the life of Susan Trinder. She was born to a mother that was mad, before she was given to a baby farmer named Grace Sucksby. Susan, called Sue, is a fingersmith and a pickpocket in order for her to help her adoptive mother earn money. One day, a man named Gentleman comes and offers her a job. Gentleman would seduce a rich, naïve woman named Maud Lilly, marry her and then send her to a madhouse after he receives her money. Sue joins in on the con, and becomes great friends with Maud, and they even develop a physical attraction. However, Sue still pushed Maud to marry the Gentleman. They run away and get married. The Gentleman calls the madhouse, who would come to fetch Maud, but the person that gets taken by them is Sue.
The second part of the book is from Maud’s perspective. Maud was an orphan, though her rich uncle took her into his care. She grew up making a bibliography of his library. Maud feels locked in the house she grew up in. One day, a man named Richard came and told her that he would help her escape, but that they would need someone that looked like her to take her place, in order for her to vanish. Maud agrees, and Sue is brought in, unknowing that Maud knows of her plan. After Maud and the gentleman are unlawfully married, they call the madhouse to get Sue. They tell them that Sue is Maud, but she has become delusional and believes that she is Sue. Maud and Richard leave to go to his house in London. However, they end up in Suckby’s house, where Maud is held prisoner and has to learn to become Sue.
Meanwhile, in the madhouse, Sue is told that she is Maud while she is heavily punished. She begins wondering of her own sanity but understands that her story is true when an old friends meets her there. They manage to escape together. Sue, back at the house, confronts Maud and wishes to kill her for what she did. The Gentleman is stabbed, before the truth is revealed. Everything was a plot for Mrs. Sucksby to receive the money. Sucksby was behind the scheme, wanting the money of both the young girls. Sucksby is hanged, and Sue finds a document that says that she is Lilly’s daughter, but they were switched at birth. The fortune was to be split between the two. Sue realizes that she was as much a pawn in the Gentleman's plan as Maud was, and they begin their relationship together.
