The narrative follows the divergent paths of a Scottish explorer and a London criminal as their lives collide during a perilous expedition to locate the source of the Niger River. Mungo Park, a man driven by scientific curiosity and the desire for discovery, navigates the harsh realities of eighteenth-century exploration. Simultaneously, Ned Rise, a survivor of London's criminal underworld, finds his fate inextricably linked to Park's quest. The story employs a dual-narrative structure, contrasting the refined, albeit dangerous, ambitions of the Enlightenment with the gritty, chaotic survival instincts of the urban poor. The world is rendered with a focus on the stark physical contrasts between the industrial grime of Britain and the untamed landscapes of Africa.

Readers frequently highlight the novel's energetic prose and its ability to balance historical detail with a irreverent, satirical tone. Discussion often centers on the stark contrast between the two protagonists, whose disparate motivations drive the narrative forward with consistent momentum. Critics often point to the author's stylistic flair as a defining feature that elevates the picaresque elements of the story. Many readers appreciate the atmospheric world-building that spans from the gutters of London to the interior of Africa, noting that the pacing remains brisk despite the dense historical setting. The work is widely regarded as a significant entry in the author's bibliography for its display of narrative ambition.