Shortly after returning to a rubber plantation in the west African jungle, overseer Worthing chats with fellow Englishman Jim Fish about life on the plantation in 1910: Harry Witzel, the plantation's cynical overseer, and his assistant, Wilbur Ashley, await the arrival of the river boat, which is taking Ashley back to England after four years of service. Although Witzel is happy to see the whining Ashley leave, he dreads meeting Ashley's replacement, who is coming in on the boat. As Witzel explains to the plantation's alcoholic doctor, the replacement will be uninformed and unprepared, and will make the same insipid comments that all the new recruits make. Witzel's predictions prove accurate, when the replacement, Langford, bounds into Witzel's bungalow full of naïve enthusiasm, uttering inane remarks about the jungle. Although Witzel, who suffers from recurring bouts of malaria, tries to warn Langford about the "damp rot" that destroys white men's souls, Langford insists he is incorruptible. That night, Langford, Witzel, the doctor, Reverend Roberts, the local missionary, Skipper, the boat's captain, and his mate Ted share a farewell feast with Ashley. During the drunken festivities, the men discuss Tondelayo, a beautiful but greedy half-caste, who roams through the area bewitching lonely white men. Witzel, who also functions as the local magistrate, has banned Tondelayo from the district and tells Langford that she is a conniving seductress. After Ashley departs on the boat, Tondelayo sneaks into Langford's bungalow and introduces herself with an enticing smile. Concerned about Langford's obvious interest in Tondelayo, Witzel has her escorted out of the jungle, but not before Langford gives her some money. Five months later, Witzel criticizes Langford for allowing sixty percent of the rubber trees under his care to die. Although Langford insists that he merely needs to become "acclimatized," a word Witzel detests, Witzel accuses him of succumbing to "damp rot." Witzel calls Langford, who has started to drink heavily, lazy and incompetent, while Langford complains that Witzel is an ineffective supervisor. Soon after, Tondelayo returns to Langford's bungalow and tries to seduce him with her dancing. Langford does his best to resist, and when Witzel suddenly appears, she hides in his bedroom. Afraid of Witzel, who used to be her lover, Tondelayo convinces Langford to meet her in the jungle the next night, then disappears. Two months later, Tondelayo and Langford finally reunite in the jungle, but she still refuses to go near Witzel. Langford decides to solve the problem, and spite Witzel at the same time, by marrying Tondelayo. Shocked that he would consider marrying not only a self-serving temptress but a half-black as well, Witzel and the other whites try to talk him out of it. Langford, however, refuses to back down, especially after he learns that Tondelayo is actually half-Egyptian and half-Arabic. Five months later, "Mrs. Langford," as Tondelayo likes to call herself, complains to her husband that he is not giving her enough bangles and silk. The bored Tondelayo then slinks into Witzel's bungalow and tries to seduce him, but he coldly informs her that she is stuck with Langford "till death do you part." Moments later, Langford sees Tondelayo struggling with Witzel and, assuming the worst, attacks him. Witzel soon knocks Langford out, impressing Tondelayo. Taking Witzel's words to heart, Tondelayo acquires some deadly "berry juice" and begins to poison her husband. The doctor assumes Langford has contracted malaria and prescribes doses of quinine, which Tondelayo replaces with berry juice. Eventually, Witzel recognizes Langford's unusual symptoms and accuses Tondelayo of poisoning her now comatose husband. Although Tondelayo protests her innocence, Witzel forces her to drink the entire vial of juice. Her fatal punishment enacted, Tondelayo runs screaming into the jungle and collapses. Later, as Skipper loads his "white cargo," the recuperating Langford and the doctor, onto his boat, Witzel greets Langford's unsuspecting replacement, Worthing. In the present, Worthing concludes his story and yells at Jim when he uses the word "acclimatized."