London, 1665. Fourteen-year-old Christopher Rowe is apprenticed to master apothecary Benedict Blackthorn. In Blackthorn’s shop, Christopher learns the delicate secrets of transforming simple ingredients into powerful medicines, potions and weapons. His beloved master guides him with a firm, steady hand—instilling in him the confidence and independence that prove increasingly vital as Christopher learns of a mysterious cult preying on the most learned men in London. The murders are growing closer and closer to home and soon Christopher is torn from the shop with only a page of cryptic clues from his master and the unambiguous warning—‘Tell no one.’

Helped by his best friend, Tom, Christopher must decipher his master’s clues, following a trail of deceit towards an unearthly secret with the power to tear the world apart.