Chapter 13 begins with O’Rourke receiving letters from people around the country after publishing an article about autoimmune disease. Though many of the letters contain wild suggestions as to what might be happening to her, several believe that she might have Lyme disease. Based on her upbringing in high-risk areas for Lyme disease, she decides to contact a practitioner named Matt Galen, who recommends a series of changes to her health regimen. Each change is to be conducted one at a time so that she can see the specific results of each change. One of his main recommendations is to begin taking low doses of naltrexone, or LDN, which helps the body to make more endorphins. O’Rourke must find another doctor to prescribe her the LDN, so she seeks out Dr. C.

Dr. C spends an hour with O’Rourke, listening to her and examining her thoroughly. O’Rourke respects Dr. C for her deep knowledge and patience. When she tries the LDN later that week, she experiences vivid nightmares, as Dr. C warned that she would, and her health gets increasingly worse; she catches a friend’s cold and has ongoing flu-like symptoms such as headaches and body aches.