Summary
In Chapter 15, Farmer shows author Tracy Kidder around Lima, Peru. The city sprawls in immense waves of building after building. Kidder's description of Carabayllo focuses on the poor, many of whom came to Lima from mountain villages of Incan heritage seeking the trappings of modern civilization and to escape the ongoing war between Peruvian military forces and the guerrilla fighters of the Shining Path (the Marxist rebellion movement). What they found was urban poverty, filth, and, increasingly, tuberculosis.

Jaime Bayona located ten Carabayallaons (residents of the slum Carabayllo) who appeared to suffer from MDR. They needed to test cultures taken from these patients, but the Peruvian national lab would not do it for Socios en Salud. Instead, Farmer flew them back to the United States to be tested. Most of those selected were infected with TB that was in fact resistant to the main drugs and most of the back up drugs. Farmer then faced three challenges: heal these ten sick people, figure how what had gone wrong in their treatment, and get them (and him) the help they all needed from governmental sources. Farmer eventually deduced that the patients were as sick as they were—and their TB as drug-resistant and dangerous to others as it was—because their doctors had followed a treatment regime slavishly and without reflection. Through continuing to treat these patients with drugs that were not working, the medical establishment had in fact bred mutated forms of TB, setting up their own later and more vicious health crisis. These policies came from the World Health Organization, and, when combined with the patients' economic conditions, were a death sentence. The doctors had done what they thought should have worked. After that, desperately poor people had to pay for their own treatments.

Analysis
Chapter 15 accomplishes several functions in the narrative. First, it quietly reintroduces Kidder as a direct observer: he has witnessed Farmer's mission in Haiti, and now does so in Peru. This lends his descriptions vivid detail, and his account marked credibility, establishing his ethos. Following Farmer gives Kidder the right and ability to talk about Farmer's thoughts and feelings, and about the suffering of the poor. He has been there to see, hear, and sympathize with them all.

Second, the descriptions of Farmer's diagnosis of the MDR TB and the problems with the official treatment regimes remind readers of another facet of Farmer. He is not just someone who cares deeply about the poor. He is an expert in TB—and someone sufficiently skilled at science and independently minded that he can see through the haze of official science.

And third, this chapter sets up Farmer's move to a still larger stage. Because the policies killing these poor people are funded by the Peruvian government (which is massively in debt to American banks) and came from the World Health Organization, to save the people of Carabayllo Farmer must move up his work to a global scale.