Stranger at the Manor — Mary Kingswood

A destitute man comes looking for help from his cousin, and uncovers some mysteries.

Phyllida Beasley is forty years old, a mousy spinster who devotes her life to caring for her brother, and doing good works in the parish. She's in a rut, but too timid to set herself free from her domineering friends and her own sense of duty. When a newcomer to the village draws her into his schemes, he challenges her to take a new direction. Can she summon the courage to step out of the shadows, when it means facing up to her terrible secret?

Peter Winslade's career as a banker is over, after his bank failed and left him destitute. He's forced to throw himself on the mercy of his cousin, the Squire, repaying his kindness by unravelling his tangled accounts. His helper is just the sort of woman he could easily fall in love with -- can he persuade her to break away and embark on a great adventure? It could be the making of her, but it could also destroy her utterly. How can he protect her from her own past?

This is a complete story with a happy ever after. Book 4 of a 6 book series.
A traditional Regency romance, drawing room rather than bedroom.