Lucinda Bromley, a botanist, has been ostracized by polite society since she was accused of murdering her fiance. As she can detect and identify almost any kind of poison, even on a dead body, she is often called on by the police to determine if a person has been killed by poison. She was very upset to discover that a Lord has been poisoned by a very rare fern, one stolen from her conservatory just a month ago. She verifies that he was indeed murdered, but does not identify the poison for the police. To protect herself, she hires fellow Arcane Society member, Caleb Jones, to track down the thief. He does identify the thief, a doctor for whom he has been searching as the doctor is attempting to copy a drug which enhances one's paranormal powers. It was originally made by a Jones ancestor, but no antidote was named. It is extremely addictive and eventually kills the user if withdrawn. Although Caleb and Lucinda are drawn to each other, he knows that insanity runs in the men of his family who have the same kind of power he has and has decided he will never marry. Although the doctor escapes, the men who had sponsored him are vanquished. She finds that the men in the Jones family have been slowly poisoned to cause the insanity. It all ends well. (Of course!)