The TV show carries over the graphic style and much of the content of the "Horrible Histories" book series. It maintains the franchise's overall irreverent but accurate focus on the dark, gruesome or scatological aspects of British and other Western world history, spanning from the Stone Age to the post-World War II era. Individual historical eras or civilisations are defined and named as in the books, with sketches from several different time periods combined within a single episode.