Dr Ulick Ford agrees to be guardian to his young cousin Petronel Fleming after her mother, Cissy, dies.  Cissy and Ulick had been engaged to be married in their youth, but she instead ran off with her drawing master, David Fleming.  Still gripped by strong feelings and struck by the resemblance to her mother, Ulick takes full responsibility for Petronel, much to the disgust of his sister, Marcia, who acts as his housekeeper.

Marcia is resentful of the growing bond between Ulick and Petronel, and seeks to undermine it at every turn.  She finally succeeds in having Petronel sent away to a Belgian boarding school.  While there, the drawing master takes a particular interest in her, and eventually reveals himself to be her father.  Pleading poverty, he gradually relieves her of all her pocket money, and then demands that she request some more from her guardian.  He becomes increasingly importunate, threatening to assert his custodial rights over her if she doesn’t comply with his wishes.  Petronel is immensely relieved when she can finally return to England.

Marcia is none too pleased at her return, and tries to marry her off to a vicar twice her age.  Petronel laughs at his proposal, declining to marry such an old man.  Ulick is thankful that the proposal was rejected, but starts to question his own feelings.  Petronel is by now a striking woman and the very image of her mother.  Ulick frets that he is even older than the unfortunate vicar – some 22 years Petronel’s senior – and fears making a fool of himself.  He is overjoyed to discover that his feelings are reciprocated, and they resolve to marry.

Unsurprisingly, Marcia is aghast at this development.  When mysterious letters start arriving for Petronel, she mischievously weaves a tale of infidelity in an attempt to derail their courtship.  The letters are actually from David Fleming, who is making aggressive demands for yet more money.  He orders Petronel to visit him in his lodgings, swearing her to secrecy.  On her arrival, he locks her in the room and makes her promise to pay him an allowance from her marriage settlement, impressing upon her a sense of filial duty.  He again threatens to assert his parental rights and forbid her marrriage.  At that moment, Ulick, having found Fleming’s letter, bursts in an apprehends him.  A traumatised Petronel explains she was doing her best to help her father.  An incandescent Ulick denounces Fleming as an imposter who assumed the identity of Petronel’s late father in order to exhort money from her.  An outpouring of contrition on his part is rewarded with a sum of money to go away for good.

Ulick and Petronel go ahead with their wedding, and we see them years later in a happy home with six healthy children.  Even Marcia has mellowed, and is enjoying the role of doting aunt.