Flint, a bitter paraplegic living in the Congo, rules a local territory by dispensing tiny amounts of sugar and liquor to the natives—often substituting kerosene for the liquor—and by staging elaborate tricks that create the illusion of supernatural powers. He operates with his fiancée, Tula, two enforcers, Hogan and Cookie, and a loyal native named Fuzzy. For eighteen years he has plotted revenge against Gregg, the man who crippled him by kicking him in the back and then ran away with Flint's wife. Flint has carved out an 80-mile circle around his jungle compound, a no-entry zone patrolled by his men where entry or exit is possible only with his consent. He also arranged years ago to have the infant daughter of Gregg and his former wife raised by nuns to be “clean in body and mind” inside a Cape Town convent. To realize his scheme, Flint sends Hogan there, disguised as a missionary, to bring the daughter, Ann, to him.
In Cape Town, Ann grows into a young woman who has suffered much; she has become a hardened alcoholic after months of confinement in a Zanzibar brothel and forced work as a prostitute. Still held at Flint’s camp, she endures daily degradation as Flint takes sadistic delight in her torment. A cynical, drug-addicted doctor named Kingsland arrives, and he and Ann soon fall in love. Flint needs Kingsland to be sober so he can operate on him and relieve the constant pain caused by his paralysis. To force sobriety, Flint has Kingsland bound with ropes, dragged to a nearby swamp, and placed up to his neck in leech-infested water so the parasites can suck the drugs or “poisons” out of his system. Despite his cruelty, Flint tolerates Ann’s relationship with Kingsland because of its purifying effect on the doctor, even as he continues to ridicule her.
After Kingsland operates on Flint, Gregg arrives at the camp, summoned by Flint, who has stolen shipments of ivory from him. Flint hopes to seal his ultimate revenge by parading a degraded Ann before Gregg, having him killed, and then sacrificing Ann as part of the natives’ funeral rite. The crippled man taunts Gregg until Gregg recognizes him as the man he once knew as Rutledge. Flint then reveals how he has abused Ann as part of his plan, but Gregg exposes Ann as Flint’s own daughter. Stunned, Flint begs Gregg not to leave the compound, warning that Fuzzy, patrolling the jungle, would shoot him if he attempted to depart. Gregg ignores the warning, leaves, and is killed by Fuzzy.
Desperate to save Ann from a sacrificial fire, Fuzzy guides Ann, Kingsland, Tula, and Cookie through an escape tunnel to the swamp. Flint stays behind and dies trying to keep the angry natives at bay, praying that Ann will escape to safety with Kingsland. Later, Flint’s pet chimpanzee is shown discovering the crippled man’s necklace among the ashes of his pyre. Meanwhile, Ann and Kingsland are aboard a riverboat, waiting to be married by the captain, as Kingsland describes their destination—a small home in Sicily.
