The story as such, ok, not bad.

But that the police let her call her alibi on her own and brief her herself? What kind of police are they?
That she potentially destroyed 230 year old items by touching them without gloves and throwing them back into the river? What kind of historian is she? And how did nobody stumble upon the apothecary's lair in 200 years? Was the house with the cellar never sold?
James being the most controlling, unhealthy partner ever? Who would even go to those lenghts? How did she never notice?

This book would probably have benefited from being proofread by a historian or researcher or something. It just feels not fully thought through at times.