The fever has started to break out and kill many people, including Polly; Mattie, Lucille, and Eliza’s servant. Many people have different theories about what it could be, but no one knows for sure.
Yellow Fever is spreading rapidly, so Mattie and her grandpa are taking precautions to stay safe and healthy. Lucille is now diagnosed with Yellow Fever, so Eliza is staying back to help take care of her.
Mattie and Grandfather set out to the country but can’t enter because they seem to have the Yellow Fever. They then go to bush hill, a hospital, and find that Mattie has Yellow Fever, so she stays there and gets nursed back to health.
Grandfather and Mattie return to Philadelphia only to find that their house has been robbed and there's barely any food. During the night robbers swarm in and in the process of stealing they kill Grandfather, leaving Mattie on her own.
Mattie finds Nell and decides to take her to Eliza’s house instead of to the orphanage. Soon Eliza’s nephews and Nell contract the Yellow Fever so Mattie and Eliza take them to the coffeehouse to nurse them back to health instead of bleeding them.
A frost has gone over the town and the fever has vanished which brings back Mother. Mattie and Eliza establish a business together and the coffeehouse returns to normal.