Cilla is the granddaughter of Johnny’s master, the silversmith Ephraim Lapham. At the book’s start, fourteen-year-old Cilla is promised to Johnny in marriage because of an economic arrangement to keep the silver shop in the Lapham family. Following Johnny’s disfigurement, however, this arrangement is cancelled. Like Rab, Cilla seems to be Johnny’s opposite in many ways. Though she is very bright, she is too self-effacing to demand to be taught how to read and write. Instead, she devotes her energy to her sickly, but beautiful, younger sister, Isannah, using any extra money she can find to buy the spoiled child ribbons and other treats. Sensitive and thoughtful, Cilla secretly sneaks food into the impoverished Johnny’s pockets in the interim period between his accident and his new home with Rab. When wealthy Lavinia Lyte becomes enchanted with Isannah, Cilla follows her sister to the Lyte home because she wants to accompany Isannah. Cilla works at the Lyte home as a lower-class servant, while Lavinia parades Isannah around Boston high society. As Lavinia cleverly tears Isannah away from Cilla, Cilla suffers silently and stoically.
On the other hand, Cilla has a caustic wit, teasing Johnny mercilessly and trading jabs with Rab. Cilla is self-reliant, a hard worker, and a kind person. Over the course of the book, Cilla develops from a skinny child into a beautiful young woman, and she begins to attract attention from men for the first time. Rab takes an interest in her, as does a young British soldier named Pumpkin, but it is Johnny that she has cared for all along. Like many colonists, she becomes an ardent Whig, and she refuses to leave for London with the rest of the Lyte household, including Isannah, on the eve of the Revolution. At the book’s end, Cilla loses her sister but gains the boy she has always loved.