Chapter 18 picks up from Chapter 16 during which Jack discovers the rickettsial infectious disease Rocky Mountain spotted fever. Rickettsias are extremely contagious and dangerous to laboratory personnel you would normally work with diagnostic samples. For this reason, rickettsia samples, like tularemia samples, are sent to a reference laboratory that has the equipment for safely working with them. In this chapter, the reference lab calls Jack directly to confirm the diagnosis of Rocky Mountain spotted fever and volunteers to report the outbreak to the city health commissioner and board.
Since Jack now has confirmation that Donald Lagenthorpe died, after hospitalization for a virtually unmanageable asthma attack, of Rocky Mountain fever, he is more convinced than ever that the something "weird" going on over at Manhattan General is peculiar to something happening at the hospital and well outside the bounds of probabilities of chance occurrences.
"Lagenthorpe expired from Rocky Mountain spotted fever," Martin said gruffly. "Find out who get the samples and who processed them."
Richard stood for a moment, obviously shocked by the news. "That means we had rickettsia in the lab," he said.
Jack bikes over to give them the news, since their lab assistants handled the Lagenthorpe samples without knowing what they were thus exposing themselves to the disease and learns that at the very moment Kelley has been called to the emergency room (ER) because two hospital staff are ill with an undiagnosed "fulminant infection." Lagenthorpe condition was also fulminant. Jack deduces correctly that the two staff work in central supply and in nursing.
Returning to the Medical Examiner building, Jack learns that the shooting victim had three bullets shot from the back during a problem with police and that Colleen and Terese have requested their presence after work at the Willow and Heather ad agency to look over the new National Health hospital advertisig campaign.