In the last jittery years of the eighteenth century, England is hungry for marvels. In rides Doctor Gustavus Katterfelto, a celebrity conjurer who once performed for Kings and now lives by his wits, with his battered stage gear and his black cat Cleo. He is joined by Roger Gossage, a young Moroccan Jew stranded in Britain. When a river accident leaves Katterfelto injured and Roger combing the Severn for lost property, he finds a dented silver horn, cold as a grave coin. When breathed into, it answers with a woman's voice - she speaks of far-off cities, strange machines and in riddles, and soon "the Oracle of Clevelode" is the sensation of the Midlands. Crowds pack Duvernet's theatre and fields at dusk. Doom-preachers chant her phrases. Rival magicians and zealots circle. But then a shadowy Constable of the Night sets a trap. As hysteria rises, Roger begins to suspect the horn is not a trick at all. In Nottingham a scientific committee is formed to test the oracle. What begins as theatre becomes obsession, and ends in a public trial for "pretending to sorcery", with Roger fighting to save Katterfelto and the voice inside the horn. Told as a breathless 'true account', The Trial of Katterfelto is a darkly comic historical fever dream about spectacle, belief, and the price of hearing the future.