Matilda Cook is a fourteen-year-old girl living in Philadelphia in 1793. Matilda’s mother, Lucille, manages the coffeehouse, and they live above the shop with Grandfather, Matilda’s deceased father’s father, who fought in the war. Matilda dreams of one day owning her own shops and traveling to Paris, but for now she helps Mother in the coffeehouse, where she is often berated for being too slow or too lazy. The coffeehouse’s cook, Eliza, is a formerly enslaved Black woman whose husband died before she could buy him his freedom. Matilda and her family also have a serving girl, Polly, who was Matilda’s childhood friend. One day, Polly fails show up at the coffeehouse. Mother goes to see where Polly is and comes back with news that Polly died from a sudden fever. Matilda feels very sad and asks to see Polly’s family or go to her funeral, but Mother doesn’t want Matilda going anywhere near a house that could contain sick people.

As Matilda serves the customers in the coffeehouse, she hears them talking about a new disease spreading around the city, and some believe it is yellow fever. More and more people continue to catch the disease and die. Mother considers sending Matilda to the Ludington family’s farm, where she will be farther away from the disease, but Matilda doesn’t want to leave. However, not long after, Mother becomes ill with the fever and insists that Matilda leave her so that she will not get sick as well. Matilda and Grandfather leave Philadelphia with a farmer and his wife to go to the Ludington farm. Grandfather begins coughing on the journey and blames it on the heat. But when the wagon is stopped by several men who are monitoring who goes in and out of the local town, the men hear Grandfather’s coughing and refuse to let him pass. The farmer leaves Grandfather and Matilda behind on the road several miles outside Philadelphia.

Matilda and Grandfather rest in the shade of a tree while Matilda thinks about what to do next. She gathers water for them to drink at a stream and collects berries for them to eat. Grandfather seems weak and at times disoriented but does not show any signs of yellow fever. After trying to find food from local farmers, Matilda returns to Grandfather and collapses. She wakes up several days later in a hospital and learns that she has yellow fever, but Grandfather does not. He explains that his recent cough was caused by heart problems. While Matilda recovers, a clerk tells her that she should go live at the orphan house since she cannot find Mother, but Grandfather protests, insisting that he’ll take care of Matilda.

Once Matilda is fully recovered, she and Grandfather return to Philadelphia. They find that the city has changed very much since they departed. Many businesses have closed. Empty houses are boarded up to prevent thieves from breaking in. When Grandfather and Matilda return to their coffeehouse, they see that it has been broken into and all of their food and several possessions have been stolen. Matilda finds some food in the withered garden and cares for Grandfather. One night, two men break into the house while Matilda is sleeping on the first floor. Matilda hides, but the men soon realize she’s there. They trap her and try to make her tell them where she’s hidden her money. Woken by the noise, Grandfather comes downstairs with his rifle and shoots. One of the men attacks Grandfather, but Matilda stabs the man in the shoulder with Grandfather’s sword, which the men had planned to steal. The men leave when Matilda threatens to kill them. Grandfather, who was knocked back by the shot of the rifle and who has already been having heart troubles, dies. Matilda brings his body outside to be buried in a mass grave the next day.

On her way home from overseeing Grandfather’s burial, Matilda sees a young girl crying. She learns that the girl’s name is Nell and that Nell’s mother is dead. While trying to find someone to take in Nell, Matilda sees Eliza in the distance and follows her until she catches up. Eliza allows Matilda and Nell to stay with her and her brother Joseph’s family. Matilda becomes attached to Nell but knows she’s not ready to take care of a child, so Matilda brings Nell to the orphan house. However, after the woman at the orphan house says they can’t take in any more children, Matilda brings Nell back to Eliza’s brother’s house, secretly relieved.

Matilda begins helping Eliza with her volunteer work for the Free African Society, caring for patients with yellow fever. One day, Matilda and Eliza return home to find that Joseph’s sons and Nell have the fever. Knowing the children need to get out of the heat to survive, Matilda and Eliza bring the children to the coffeehouse, where it is cooler. The first frost soon arrives, an event that people believe will bring an end to the epidemic. The children eventually recover.

After the epidemic ends, Matilda reopens the coffeehouse with Eliza as her partner and begins spending more time with a local painter’s apprentice, Nathaniel Benson. One day, Nathaniel comes in the coffeehouse to announce that President Washington has returned to Philadelphia. Everyone rushes outside to catch a glimpse of the president. On their way back to the coffeehouse, a carriage arrives and Matilda’s mother steps out. Mother left for the Ludington farm shortly after Matilda and Grandfather did and tried to track them down when she realized they were not there, which only made her weaker. She recovered at the Ludingtons’ and returned to Philadelphia as soon as she could. With Mother needing more rest than before, Matilda continues running the coffeehouse and caring for Nell as the city moves on from the epidemic.