Toronto author Kevin Sands holds two degrees in theoretical physics, so naturally his first novel is about … 17th-century alchemy. Not just alchemy, but also dark conspiracies, political intrigue, mysterious codes, murder, and early treatments for asthma. Instead of writing, say, the kidlit version of Interstellar, Sands plunks readers down amid the sights and smells of 1667 London, less than a decade after the death of Oliver Cromwell and the restoration to the throne of Charles II. The charged political atmosphere helps drive the plot, but as with most of the other historical elements in this speedy and often graphically violent historical thriller, the veracity of the details is less important than the push to deliver big payouts on both sides of that genre label. The Blackthorn Key is a novel filled with history and explosions, and it’s the latter that are more memorable, by far.

The story begins with an explosion. Fourteen-year-old Christopher Rowe, an apothecary’s apprentice with a knack for cracking codes and a taste for risky schemes, has worked out his master’s recipe for gunpowder. Naturally, he builds a cannon and nearly blows his own head off. His accomplice is his buddy Tom Bailey, the baker’s son. Christopher and Tom’s friendship has a distinctly Harry/Ron dynamic to it – one is charismatic and resourceful, the other headstrong and loyal.

Christopher’s master is the brilliant and endlessly patient Benedict Blackthorn (Dumbledore, basically, if we’re continuing with the Potter comparison). He is one of the era’s many apothecaries, mixing herbal remedies and concoctions in his shop, and experimenting with a kind of proto-chemistry. He is also (unlike most apothecaries) exceedingly nice and generous to his apprentice, and has taught him much – not only about the trade, but about the code-making and -breaking that goes into protecting that trade’s secrets.
Even as Christopher and Tom benignly razz each other and get up to no good, England’s apothecaries are being brutally murdered, allegedly by a shadowy group that wishes to overthrow the monarchy. The young apprentice’s various skills are tested when his master becomes the next victim, and he finds himself homeless and hunted. To uncover the truth of what is going on, Christopher must decipher Blackthorn’s final message to him, which is rendered in fiendishly difficult code.

Christopher’s attempts to crack the code while evading both the killers and authorities comprise the bulk of the story. Sands moves the narrative along at a heart-racing pace, which makes for a fun and absorbing read, though it does mean few of the characters are well developed and the historical background often becomes incidental. His decision to kill off Blackthorn early is a bold one, but robs the book of its one complex adult character. As a result, the novel’s big-bang climax does not quite have the pop it should, since other than Christopher and Tom, we know (and care) very little about the motivations of the various good guys and bad guys who round out the cast.
Where Sands is most effective is in the obvious delight he takes in creating codes for Christopher (and the reader) to crack, and in finding endlessly entertaining ways to show off the apothecary’s art. This is where his scientific background connects to the themes of the book: as he notes in the preface, all of the concoctions he depicts are real, many are dangerous, and some are lethal.

The Blackthorn Key is a tightly packed bomb of a book that goes off in a way that might be messy, but is satisfyingly loud.