In the 1830s, decades before Darwin published the Origin of Species, a museum of evolution flourished in London. Reign of the Beast pieces together the extraordinary story of this lost working-man's institution and its enigmatic owner, the wine merchant W. D. Saull. A financial backer of the anti-clerical Richard Carlile, the ‘Devil's Chaplain’ Robert Taylor, and socialist Robert Owen, Saull outraged polite society by putting humanity’s ape ancestry on display. He weaponized his museum fossils and empowered artisans with a knowledge of deep geological time that undermined the Creationist base of the Anglican state. His geology museum, called the biggest in Britain, housed over 20,000 fossils, including famous dinosaurs. Saull was indicted for blasphemy and reviled during his lifetime. After his death in 1855, his museum was demolished and he was expunged from the collective memory. Now multi-award-winning author Adrian Desmond undertakes a thorough reading of Home Office spy reports and subversive street prints to re-establish Saull's pivotal place at the intersection of the history of geology, atheism, socialism, and working-class radicalism.