The Perfect Poison. Number 6 in series

Plagued by rumours that she poisoned her fiance, Lucinda Bromley manages to live on the fringes of polite society, tending her beloved plants - and occasionally consulting on a murder investigation. For the notorious botanist possesses a unique talent: she can detect almost any type of poison. But the death of a lord has shaken Lucinda to her core. At the murder scene, she picks up traces of a poison containing a very rare species of fern - stolen from her conservatory just last month.
To keep her name out of the investigation, and to find the murderer, Lucinda hires fellow Arcane Society member, Caleb Jones. As a nearly overwhelming desire blooms between them, they are drawn into a deadly conspiracy that can be traced to the early days of the Arcane Society - and to a legacy of madness that could plunge Caleb into the depths of his own tortured soul...