Face Down upon an Herbal — Kathy Lynn Emerson

When a dead body is found in a castle library, Elizabethan herbalist Susanna, Lady Appleton, investigates a mystery that mixes passion and deadly ambition into a potent brew....

FACE DOWN UPON AN HERBAL
Luxurious Madderly Castle hosts velvet tapestries, hidden doors, slinking servants...and a murdered houseguest, Baron Glenelg. Ordered by Queen Elizabeth to help chatelaine Eleanor Madderly complete a new book on botanical decoctions, Susanna soon realizes there is more to the royal request when she finds out the victim was face down upon an herbal--the very one she herself authored. And when one lady and then another perish in a brutal manner, Susanna must unmask the killer quickly, before she becomes the next to die...