The Coca Bums

Set in Peru in 1985, the novel is narrated from the viewpoint of Jim Hiram, an American businessman, asked by Helen Seymour, a wealthy Philadelphian, to find her wayward brother, Peter. He had fled to Peru to avoid lawsuits filed by his father to have him declared incompetent because of cocaine addiction and incursion of high debts. Her last word from Pete was a postcard from Tingo Maria, a center of the cocaine trade and Maoist Sendero Luminoso rebel activity. When she turns on the charm, Jim reluctantly agrees to the search. A sister trading intimacy for her brother's safety is a variation on that theme in Measure for Measure, though the treatment is not so dark since they're mutually attracted and are modern in outlook, not Elizabethan. When her parents arrive with their own detective, and the father has a heart attack in the Andes, the plot complicates and their love is strongly tested before they come through it together.