In the late-eighteenth century, the conjurer and amateur scientist Gustavus Katterfelto has made a name for himself travelling across the English countryside with a bag of tricks. For audiences, his astonishing stunts are pure magic. For Katterfelto, each one is carefully engineered and executed with the help of his colleague, confidante and amanuensis, and our narrator, Roger Gossage. Yet one day in their travels, the two men come across a mystifying object beyond their ken: a metal horn that emits a disembodied woman's voice. She calls herself Siri of Toronto, and claims to speak from a place plagued by climate catastrophe and social unrest. As they begin to use the horn in their magic shows, Gossage and Katterfelto must work to understand the origin and intent of Siri's call -- a quest that will put them up against the limits of reason and test Roger's allegiance to the man he calls his friend. Endlessly inventive, richly imagined, and entirely its own, The Trial of Katterfelto is a consciousness-expanding novel that writes directly into the most urgent questions we face as a species: who we are, what we have done, and what we might do from here.