In 1795, Scottish explorer Mungo Park is sent to western Africa to find the Niger River, which no European has ever seen. Mungo is the fourth adventurer dispatched by the African Association for Promoting Exploration, a group of wealthy Englishmen intent upon expanding knowledge of uncharted regions. His task is made difficult by geography, climate, and the frequent hostility of the Africans. Captured by the Moorish potentate Ali, Mungo is about to be blinded by Dassoud, Ali’s henchman, when he is saved by Johnson, his guide and interpreter. Born Katunga Oyo, Johnson is a former South Carolina slave who became the London valet to Sir Reginald Durfeys and learned to love the world of English writers such as John Milton and Alexander Pope. After killing a gentleman in a duel, Johnson was transported back to Africa, where he escaped and joined up with Mungo.
Back in London, Ned Rise, a lowborn Londoner, survives by his wits, and Ailie Anderson, Mungo’s longtime fiancé, waits for Mungo to return from Africa. Ned earns money in a tavern by staging a show featuring a black servant having sex with two prostitutes. Ailie, the daughter of a physician in Selkirk, Scotland, longs for Mungo’s return and must resist the attentions of Georgie Gleg, her father’s assistant.
Ned is the illegitimate son of Sarah Colquhoun, an alcoholic. As a youth, he was tortured by Edward Pin, Sarah’s lover, who cut off the boy’s fingertips to make him a better street beggar. After Pin was killed, Ned lived on the streets. At twelve, he was taken in by Prentiss Barrenboyne, a wealthy bachelor who taught him to play the clarinet. Ned lived with Barrenboyne for seven years, until his benefactor was killed in a duel with Johnson. A life of living by his wits has led to the sex show. When police raid it, Ned plunges into the icy Thames River, the first of two times he will be assumed to be dead.
Rescued from the river by two fishermen, Ned begins selling what he passes off as authentic Russian caviar. He must assume disguises to hide from those arrested in or socially embarrassed by the sex-show raid. Ned especially wants to avoid Smirke, the landlord of the tavern, who would kill him without hesitation. When he is recognized by Billy Boyles, he enlists his old friend in the caviar scam.
In Africa, Johnson and Mungo are taken on a journey into the desert. They escape and make their way to Segu, which sits on the west bank of the Niger. Because the African Association, directed by Sir Joseph Banks, knows Africa only from sixteenth century maps, Mungo’s discovery of the river will change the European perception of the continent. During his London days, Johnson told several members of the association about Africa, but they have no faith in the words of their racial “inferior.” Even Mungo cannot shake his view of Johnson as a savage because his guide rejects the Bible.
Back in Scotland, Gleg gives Ailie a microscope, stimulating her enthusiasm for making scientific sketches of minutia. Mungo grows weary of exploring and of Africa. When Johnson is apparently eaten by a...