"The Blackthorn Key Series" is a historical adventure book series written by Kevin Sands. Set in 17th-century London, it follows the story of a young apprentice named Christopher Rowe, who works for a skilled apothecary. The series combines elements of mystery, science, and alchemy as Christopher uncovers secrets and solves puzzles while navigating a world filled with danger. Throughout the series, Christopher faces various challenges, including rival apothecaries and sinister plots. The books are known for their engaging storytelling and rich historical detail, making them appealing to both young readers and adults interested in adventure and history.