The Valet Experiment by Ellie St. Clair

How does he ever protect a woman whose greatest danger is herself?

Jemima St. Vincent may now live in one of the finest homes in London, but she hasn’t let that change anything. She is still going to become a renowned chemist — even if she has to put out a few fires along the way. At the age of twenty-six, she is determined to support herself, as it has become abundantly clear that no man wishes to marry the peculiar sister of a man with no fortune — even if he is a duke.

As the valet — and best friend — of a new member of the nobility, Archie Thompkins has come a long way from his humble beginnings. But that doesn’t mean he will ever feel at ease in the new life he has assumed, particularly when secrets from his past come back to haunt him. The only way to cope is to do what he has always done best — protect those he loves.
Archie agrees to look after his best friend’s sister, despite their aggravation toward one another and her insistence she is fine on her own. No one is more shocked than the two of them when the sparks between them begin to burn much differently. But when Archie’s own past begins to threaten Jemima, he must decide if she is more at risk with or without him. Jemima is up for playing with fire — if only the stubborn man will let her.