Thirteen-year-old Lyddie Worthen lives with her brother, Charlie, her sisters, Rachel and Agnes, and her mother in a cabin on a small Vermont farm in 1843. As their story begins, a black bear finds its way into the cabin. Lyddie quietly tells the family to climb into the loft, and she stares the bear down until they are safe. Then she scrambles up, too. The bear makes a mess but hurts no one, and the siblings laugh. Lyddie and Charlie clean up, but their mother decides they will leave the farm. Charlie takes his mother, Rachel, and Agnes to the home of Uncle Jonah and Aunt Clarissa and then returns to help Lyddie take care of their home. They stay together all winter and even celebrate the birth of a new calf, but then their mother writes to tell them that she has rented out the farm and has hired Charlie out to the mill and Lyddie to Cutler’s Tavern.

On their way to their new homes, Lyddie and Charlie stop at the farm of their neighbor, Quaker Stevens. Stevens buys the calf, gives the children a meal, and tells his son Luke to drive them to the village. Lyddie does not know whether to laugh or cry as she says goodbye to her brother and finds herself alone.

After some initial challenges, Lyddie settles into her new job at Cutler’s Tavern. She works hard and becomes friendly with the cook, Triphena. The mistress, however, is harsh, and Lyddie sleeps in a small, windowless passage. A guest tells Lyddie about her factory work in Lowell, Massachusetts, and Lyddie thinks she is lying about how much money she makes. Lyddie herself counts the money from the sale of the calf over and over for comfort as she slowly loses her connection with her family. Even when Charlie visits, the siblings have little to say and no privacy in which to say it.

When spring arrives, Lyddie returns to the cabin overnight and finds a fugitive slave named Ezekial hiding there. Lyddie has always thought that she would turn in a runaway for the reward money, but after getting to know Ezekial, she no longer wants to. Instead, she gives Ezekial the money from the calf so he can continue his journey to freedom and eventually help his family join him. When Lyddie goes back to the tavern, the mistress fires her for her unauthorized absence, and Lyddie decides to go to Lowell to take a job in the mills.

In Lowell, Lyddie gets a job with the Concord Manufacturing Corporation and settles into a company boardinghouse run by Mrs. Bedlow. Lyddie rooms with Amelia, Betsy, and Prudence; on the job, she is patiently trained by Diana Gross, a labor activist. Betsy begins reading to the exhausted Lyddie after the latter’s first full day on the job, and Lyddie discovers the power of stories and reading through the novel Oliver Twist, which comes alive as she reflects on the characters and events of the tale and applies them to her own life. When her roommates leave for their July vacation, Lyddie decides that she will use Oliver Twist to learn to read better. She even purchases her own copy.

As the weeks and months pass, Lyddie becomes more and more adept at her job, operating extra looms and increasing her production. She wants to save enough money to pay off her father’s debt and reunite her family on the farm. The company continually increases the speed of its machines, and many girls cannot handle the pace. Lyddie has no trouble and cannot understand the importance of the petition for ten-hour days that Diana is promoting. Lyddie simply wants to make more money, even though she worries that she might become a slave like in the song Betsy sings.

The machines speed up more and more, and conditions at the mill deteriorate. Many workers leave, but the company replaces them with lower paid Irish Catholic girls. Lyddie works so hard that she becomes something of a machine herself. She pays little attention to anything else and even stops studying Oliver Twist. She is simply happy that her bank account is growing. Lyddie then suffers a setback when she is hit in the head with a shuttle.

When Lyddie returns to work after the accident, the overseer, Mr. Marsden, puts her in charge of Brigid, a new girl. Lyddie becomes frustrated and impatient with Brigid, who makes many mistakes and tends to cry when she is overwhelmed. Changes are happening at the boardinghouse as well—Amelia can no longer keep up with the pace and goes home, and Betsy’s cough worsens to the point that she, too, must leave Lowell.

One day, Lyddie finds Luke Stevens waiting for her at the boardinghouse with a parcel from Ezekial, who is now free and who has returned her money with interest. Soon after, another visitor arrives, Lyddie’s Uncle Judah, who informs her that her mother is in an asylum and that he will be selling the farm to pay for her care. He also brings Lyddie’s only surviving sister, Rachel, to her. Rachel is small and silent, and Lyddie is not sure how to care for her, especially since Mrs. Bedlow has to bend the rules to keep Rachel at the boardinghouse.

Before she can make any decisions about Rachel’s care, Lyddie is struck with a fever that keeps her in bed for many days. Rachel, Mrs. Bedlow, Diana, and Brigid care for Lyddie, who eventually recovers, though she is weak when she finally goes back to work. After Lyddie is well, Rachel takes a job as a doffer in the mill. The sisters have received a letter from Charlie indicating that Quaker Stevens will try to help, but their uncle remains adamant about selling the farm. Unfortunately, Rachel soon develops a cough similar to Betsy’s.

Charlie finally arrives in Lowell to visit Lyddie and Rachel. He is now a full apprentice at the mill and has found a family with the Phinneys, who also want Rachel to live with them. Lyddie struggles to let Rachel go, but she knows she must for her health and happiness. She also has no choice but to allow her uncle to sell the farm. Charlie gives Lyddie a letter from Luke Stevens that contains a proposal of marriage, but Lyddie burns it.

After Rachel leaves, Lyddie feels more alone than ever. Even Diana leaves Lowell after becoming pregnant with the child of a married man. Lyddie begins teaching Brigid, who has finally become efficient on the job, how to read and write. One day, though, Lyddie goes back to the weaving room to look for Brigid and discovers Mr. Marsden assaulting the girl. Lyddie slams a buck of water into his head and rescues Brigid, but the next day, Lyddie is dismissed from her job due to Mr. Marsden’s accusation of “moral turpitude.”

Lyddie, after she finally realizes what “moral turpitude” means, is indignant. To protect Brigid, she writes a letter to Mr. Marsden’s wife that Brigid is to mail immediately if she has further trouble with Mr. Marsden. Lyddie then leaves Lowell. She visits Diana in Boston before going home to Vermont, unsure what she will do with her life. At the cabin, Lyddie meets Luke and finally realizes that she longs to go to college and no longer be a slave to anyone, especially herself. She also discovers that she could love Luke and hopes he will wait for her as she pursues her dreams at Oberlin.