Miss Prism seems at first a minor figure in Oscar Wilde's The Importance of Being Earnest, a prim governess in the country subplot. In fact she is indispensable, for she holds the secret that resolves the entire comedy, and she also serves Wilde's satire on Victorian respectability. Her importance is therefore both structural and thematic.
Guardian of the plot's great secret. Years before the action begins, Miss Prism was the nursemaid in the Moncrieff household. In a moment of absent-mindedness she placed the manuscript of her three-volume novel in the perambulator and the baby in a large handbag, which she then abandoned at the cloakroom of Victoria Station. That lost baby is Jack Worthing. Miss Prism alone carries the knowledge that unlocks his origins, so the whole mystery of identity depends on her.
Agent of the denouement. The play's tangled confusions are untied only when Lady Bracknell recognises Miss Prism and demands the return of the missing infant. Confronted with the very handbag, Miss Prism identifies it, and Jack is revealed to be Lady Bracknell's nephew, Algernon's elder brother, and truly named Ernest after his father, General Moncrieff. Every knot of the plot, Jack's parentage, his right to marry Gwendolen, and the comic truth of the name "Ernest", is loosed through her. Without Miss Prism there is no resolution.
A target of Wilde's satire. Miss Prism embodies the earnest, moralising respectability that Wilde loves to mock. She preaches propriety and duty to her pupil Cecily and condemns the wayward, yet she herself once lost a baby through carelessness and harbours romantic feelings for the clergyman, Dr. Chasuble. The gap between her severe morality and her comic past exposes the hypocrisy of Victorian virtue.
Comic sub-plot and pairing. Her flirtation with Canon Chasuble supplies a gently ridiculous romance among the older characters, balancing the young lovers and adding to the play's web of courtships. Their pairing rounds off the general movement toward marriage.
Conclusion. Miss Prism is far more important than her modest role suggests. As the keeper of the handbag secret she is the mechanism that resolves the plot, and as a moralising governess with a scandalous lapse she embodies Wilde's satire on respectable hypocrisy. She is the small hinge on which the whole comedy finally turns.