Throughout her lifetime, Jane Austen wrote countless letters to her sister. But why did Cassandra burn them all?

1840: twenty three years after the death of her famous sister Jane, Cassandra Austen returns to the village of Kintbury, and the home of her family's friends, the Fowles.

She knows that, in some dusty corner of the sprawling vicarage, there is a cache of family letters which hold secrets she can never allow to be revealed.

As Cassandra recalls her youth and her relationship with her brilliant yet complex sister, she pieces together buried truths about Jane's history, and her own. And she faces a stark choice: should she act to protect Jane's reputation, or leave the contents of the letters to go unguarded into posterity?