Charlotte Heywood first came to Sanditon as the result of a happy accident, when she helped the Parkers after their carriage lost a wheel. Now she is returning due to a tragedy: Sidney Parker, her erstwhile lover, has died of yellow fever in Antigua.
Sidney was the guardian of Charlotte’s heiress friend Georgiana Lambe; that guardianship has now transferred to his brother Tom, who worries that Georgiana will never accept a suitor—she dismisses them all as substanceless and money-grubbing. Tom’s wife Mary suggests that Georgiana needs the company of a friend, and so the Parker carriage once again brings Charlotte to the seaside town, this time with her sister Alison in tow.
They are greeted by Tom, Mary, and Tom’s brother Arthur, who is now Tom’s aide in developing Sanditon into a fashionable resort. (When Arthur returned to Sanditon without his sister Diana, his hypochondria seemed to be cured. He suspects his new sense of purpose—helping his brother—is the cause.) The Parkers were surprised to hear Sidney was in Antigua; they have asked the agent gathering Sidney’s things to discover why he was there.
Tom is excited by the impending arrival in Sanditon of a company of soldiers, whom he hopes will spend plenty of money, thus helping him to repay Sidney’s wealthy widow Eliza, who currently owns a large portion of Sanditon because Sidney covered Tom’s debts before his death.
Charlotte, Alison, and Georgiana go to tour the soldiers’ encampment and meet the officer in charge, Colonel Lennox, and his subordinate Captain Fraser. Lennox is taken by Charlotte, and Alison encourages the connection—she wants to find husbands for both herself and Charlotte in Sanditon, especially so that Charlotte isn’t trapped into a marriage with a dull farmer back home who is ready to propose. To that end, Alison is eager for the soldier’s parade the next day, and wants to look her best—her idea of romance is drawn from books.
At the parade, Charlotte is reacquainted with Lady Denham and her niece Esther, who is visiting while her new husband Lord Babington is away. Esther is recovering from a miscarriage and was told that trying to have another baby could be fatal, but she is determined to give Babington an heir, and hopes the sea air will cure her. She lies in a letter to Babington that Sanditon’s Dr. Fuchs is confident about her prospects. She’s also shocked to note that her scheming stepbrother Edward is amongst the company of soldiers.
Lady Denham is, as ever, brutally candid in her interactions, including in her dismissal of a sugar boycott initiated by Georgiana and proselytized by her chaperones the Hankinses in order to press for the abolition of slavery in overseas territories.
Georgiana and Arthur avoid the parade, as does the eccentric artist Charles Lockhart, a new resident of Sanditon. Arthur and Charles dislike the military, but Charles does find Georgiana intriguing, especially when she openly disdains his pride and earnestness. Arthur, whom Georgiana takes as a model of a possible husband, smiles.
As the soldiers pass, a little boy dashes after them and falls into the street. Charlotte saves the child from trampling by a horse, and takes him and his older companion to the Parkers to dress a cut shin. Turns out the boy “Leo” is actually Leonora, and her companion is her brooding cousin Augusta Markham. Charlotte accompanies them home to a wealthy estate, where she learns that a governess is needed for the motherless girls.
They don’t get along with each other and are rude to Charlotte. Augusta hates living with her uncle, Leonora’s father, at the estate. Charlotte learns from the Parkers that his name is Alexander Colbourne. Tom calls him a recluse and miser, always obstructing Tom’s attempts to improve Sanditon. He withdrew from society after the death of his wife.
Colonel Lennox stops in to the Parkers’ to make sure that Leonora is okay, and stays for tea. Alison works overtime to commend Charlotte to him, leading Charlotte to suddenly excuse herself and leave. She goes to church and lights a candle for Sidney. When she returns, Alison apologizes; she does understand that Charlotte is still in love with Sidney, but wants to help her move on. Charlotte explains that she has realized that she never wants to be under a man’s power—and so she will not get married. Instead, to the horror of her sister and Mary and the disappointment of Georgiana, she will become a governess, to make her own living.
She returns to the Colbourne estate to interview with Alexander, who quickly quizzes her on her accomplishments but argues against her intention to thoroughly educate his daughter and niece. I know what happens to women who don’t meet society’s expectations, he says. Charlotte walks out, telling him that if he doesn’t want his charges to become learned and independent than she’s not the woman for the job. He eventually rides after her, gives her the job, and rides away.
Alison also has a dramatic encounter. Georgiana takes a would-be suitor’s carriage for a ride along the beach with Alison, circling a group of soldiers. But a wheel breaks, sending the young women to the sand. Alison opens her eyes to a dashing soldier, Captain William Carter, bending over her, to her delight.
A less pleasant encounter occurs between Edward and Esther when he comes to visit Lady Denham, who warns him to keep his distance, especially from Esther. Esther herself dismisses Edward, and he promises to stay away. But, despite his claim to Lady Denham that his appearance in Sanditon is a coincidence, he was the one to suggest it as a location to Colonel Lennox, and he’s already racking up gambling debts. Esther fears that Lady Denham will fall for Edward’s charm, and extends her stay.
More surprising news reaches the Parkers. Sidney wasn’t in Antigua on his own affairs. He was there on behalf of Georgiana.