Can you please briefly summarize Chapter 21 of Contagion by Robin Cook?
Chapter 21 opens on Saturday morning at Terese's apartment where she woke Jack periodically per doctor's orders to check for signs of neurological damage after being knocked out cold. Terese goes off to the ad agency in view of her looming Monday morning deadline and Jack goes home on the subway to face his vandalized apartment. After an attempt at tidying it, he goes in to the Medical Examiner's building because the cases at Manhattan General's emergency room the day before are worrying him.
He finds that Laurie is the weekend doctor in charge of autopsies and that all three sick hospital employees, whom he left as patients at General, were now patients on slabs with the medical examiners and were awaiting postmortem autopsies. Laurie is in the middle of her third autopsy when Jack joins her in the autopsy theater. The new she gives him is that all three women--one a lab assistant, one a nurse, and one in central hospital supply--died of Rocky Mountain spotted fever, the third infectious disease to break out in Manhattan General in less than a week.
Nancy Wiggens had been brought in at four A.M.! The provisional diagnosis was Rocky Mountain spotted fever.
Jack found two more cases with the same diagnosis: Valerie Schafer, ... and Carmen Chavez ....
Jack then gets an invitation from Laurie to a dinner party before he works through some of his backlog of paper work. With the dinner invitation pushed to the sides of his mind, jack goes home for a vigorous turn on the basketball court. Here Warren questions him about his sudden curiousness about a gang and quizzes him about why his jaw was "banged up."
Feeling particularly lonely after the unexpected kindnesses he received from Terese and then Laurie and finding nothing left in his refrigerator except moldy cheddar cheese and old eggs, Jack took a chance on calling Terese at the ad agency for possible dinner out, which she declined begging her deadline as a valid excuse. With the loneliness still gnawing, Jack calls Laurie to accept the dinner party invitation.