After uncovering Mary Austen's lies, Cassandra's determination to keep Jane's letters private is stronger than ever. Her mission is accompanied by a second – to secure a home for Isabella, who, following the death of her father, is being forced to leave the vicarage.

Intimations of a past romantic rivalry between young sisters Cassandra and Jane threaten to emerge. The older Cassandra denies any such thing, but as she delves into Jane's old letters, she secretly re-lives the youthful days of her and Jane's first encounter with Henry Hobday.

Mr Dundas and his wife prepare to move into the Kintbury vicarage, and the urgent question of Isabella's future continues to occupy Cassandra as she learns the truth about Isabella and Lidderdale's past. Dinah makes a reckless decision. The letters reveal her sister's struggle to keep writing, as the family's fortunes – and Jane's mental and physical health – went into an alarming decline. Amid these very private recollections, young Cassandra's own letters tell a heartbreaking story of just how much she sacrificed to support her sister.