Man and Wife was Wilkie Collins’ ninth published novel. It is the second of his novels (after No Name) in which social questions provide the main impetus of the plot. Collins increasingly used his novels to explore social abuses, which according to critics tends to detract from their qualities as fiction. The social issue which drives the plot is the state of Scots marriage law; at the time the novel was written, any couple who were legally entitled to marry and who asserted that they were married before witnesses, or in writing, were regarded in Scotland as being married in law.
The novel has a complex plot, common in Collins’ work. In a Prologue, a selfish and ambitious man casts off his wife in order to marry a wealthier and better-connected woman, by taking advantage of a loophole in the marriage laws of Ireland.
The initial action takes place in the widowed Lady Lundie's house in Scotland. Geoffrey Delamayn has promised marriage to his lover Anne Silvester (governess to Lady Lundie's stepdaughter Blanche), who has incurred the enmity of her employer. The spendthrift Geoffrey is about to be disinherited and wishes to escape from his promise and marry a wealthy wife. Nevertheless, he is obliged to arrange a rendezvous with Anne, in the character of his wife, at an inn, and documents this in an exchange of notes with her. Subsequently, urgent matters force him to send his friend Arnold Brinkworth, Blanche's fiancé, to Anne in his place. To gain access to her, Arnold must ask for "his wife". Although nothing improper passes between them, they appear to the landlady and to Bishopriggs, a waiter, to be man and wife.
Thus, both Geoffrey and Arnold might be deemed to be married to Anne, depending on the weight put on the spoken and written evidence. Most of the novel concerns Anne's, Geoffrey's and Arnold's attempts to clarify their marital status:
In subsequent chapters Geoffrey, a keen athlete, courts Mrs Glenarm, a wealthy young widow, while Anne consults lawyers who give her conflicting advice about her position, and later tries to explain the situation to Mrs Glenarm, who rebuffs her. Arnold seeks the advice of Lady Lundie’s brother-in-law Sir Patrick Lundie, a retired lawyer. Sir Patrick approaches the problem with energy, but owing to various mishaps, Geoffrey’s determination that his scheme shall succeed, and the unsatisfactory state of the law, is not immediately successful. However, he ascertains that the correspondence linking Geoffrey and Anne exists and was stolen at the inn by Bishopriggs, who tries to extort money for it. Anne, who strongly wishes to remove any impediment to Blanche and Arnold’s marriage, comes to the same conclusion and forces Bishopriggs to give her the letter by threatening to reveal its contents, which would make it worthless for blackmail. Eventually Anne offers to reveal her relations with Geoffrey, even at the cost of her reputation – impressing Sir Patrick with her courageous and honourable behaviour. At a meeting of all the parties and their lawyers, she makes her revelations. Geoffrey can no longer avoid honouring his promise to her and acknowledges her as his wife.