Miss Sarah Fry is described in Sharpe's Escape as being "twenty-two years old, blue-eyed, fair-haired, and worried for her future."

When she was ten, her father died, and her mother died a year later. She was subsequently raised by an uncle who had reluctantly paid for her schooling, but refused to provide any kind of dowry when she had reached 18, therefore cutting her off "from the more lucrative part of the marriage market".

She became a nursery maid for the children of an English diplomat who had been posted to Lisbon, and it was there that the wife of Major Ferreira offered to double her salary if she would come to Coimbra to school her two children, Tomas and Maria Ferreira. Without the money to pay her fare back to England, and a glowing testimonial from her previous employers, she was trapped in Coimbra with the Ferreria family.

When they fled the advancing armies, Major Ferreria's brother Farragus, a criminal, contrived to trap her in the house where he beat and stripped her in advanced of a planned rape, but she was rescued by billeting officer Richard Sharpe whom she accompanied on a search of Farragus' illegal warehouse. They were attacked and forced to escape, naked, in the pitch dark, through the sewers. 

When she, Sharpe, Harper, and a Portuguese girl, Joana, were safely away, they hid themselves in a cottage to wash and rest. She was complimented by Sharpe for never once complaining. They slept together that night, and the following day she saved him from a French officer who had stopped to sketch Sharpe's portrait as he dozed in the doorway. Sarah kept the picture.

Eventually, they caught up with the British forces and Farregus was killed, Sharpe made sure the criminal's loot was given to Sarah, and declared it her property.