The novel is a first-person narrative told from the point of view of the adolescent girl Maud Ruthyn, an heiress living with her sombre, reclusive father Austin Ruthyn in their mansion at Knowl. Through her father and her worldly, cheerful cousin, Lady Monica Knollys, she gradually learns more regarding her uncle, Silas Ruthyn, a black sheep of the family whom she has never met; once an infamous rake and gambler, he is now apparently a fervently reformed Christian. His reputation has been tainted by the suspicious suicide of a man to whom Silas owed an enormous gambling debt, which took place within a locked, apparently impenetrable room in Uncle Silas's mansion at Bartram-Haugh.In the first part of the novel, Maud's father hires a French governess, Madame de la Rougierre, as a companion for her. Madame terrifies Maud and appears to have designs on her; during two of their walks together, Maud is brought into suspicious contact with strangers that seem to be known to Madame. (In a cutaway scene that breaks the first-person narrative, we learn that she is in league with Silas's good-for-nothing son Dudley.) The governess is eventually dismissed when she is discovered by Maud in the act of burgling her father's desk.Maud is asked in obscure terms by her father if she is willing to undergo some kind of "ordeal" to clear the name of her uncle, and of the family more generally; shortly after she assents, he dies. At the reading of his will, it emerges that her father added a codicil to it: Maud is to stay with Silas until she comes of age; if she dies whilst still a minor, the estate will pass to Silas. Lady Knollys, together with Austin's executor and fellow Swedenborgian, Dr. Bryerly, attempt in vain to overturn the codicil, realizing its many dangerous implications for the young heiress; despite their efforts, Maud consents willingly to spending the next three and a half years at Bartram-Haugh.Maud initially finds life at Bartram-Haugh strange but not unpleasant, despite ominous signs such as the uniformly unfriendly servants and a malevolent factotum of Silas's, the one-legged Dickon Hawkes. Silas himself frightens Maud but is nonetheless seemingly kind to her, in contrast to his treatment of his own children, the loutish Dudley and the uneducated Millicent ('Milly'). Although Maud initially deprecates Millicent's rustic mannerisms they become best friends, and each other's only source of companionship at the estate. During her stay, Maud is subject to various attempts by Dudley to court her, but she rejects him thoroughly on each occasion. Silas is periodically subject to mysterious catatonic fits, attributed to his massive opium consumption.