Molly Ayer is a seventeen-year-old girl who lives with her foster parents, Ralph and Dina Thibodeaus, in the town of Spruce Harbor, Maine. Even though Dina constantly criticizes Molly for her liberal opinions and “goth” self-presentation, Molly knows that Ralph and Dina give her a better, safer home than many of her previous foster families. As the novel progresses, it is revealed that Molly grew up on Indian Island, a Penobscot reservation. Molly’s father died in a car accident when she was eight years old, and her mother, Donna Ayer, was soon jailed for charges related to drug abuse. Molly’s only link to her parents is the charm necklace her father gave her for her eighth birthday.
After stealing a library copy of Jane Eyre, Molly is sentenced to fifty community service hours. Her boyfriend, Jack, arranges for her to fulfill her hours by helping Vivian Daly, the elderly, lonely woman his mother Terry housekeeps for, to clean out her cluttered attic. Despite her anxiety around letting Jack help her, Molly agrees because she is afraid of being sent to juvenile detention or being kicked out by Ralph and Dina. The only catch is that Terry and Jack have lied to Vivian, telling her that Molly’s community service hours are for a school project.
The novel’s parallel storyline begins in 1929 and features Vivian’s life story as Niamh Power, a nine-year-old girl who lives in New York with her father, Patrick, her mother, Mary, her younger twin brothers, James and Dominick, and her baby sister, Maisie. Two years before, Niamh and her family emigrated from Kinvara in County Galway, Ireland. In New York, Niamh’s depressed mother and alcoholic father struggle to provide for their children. One night, there is a house fire that kills Niamh’s father and brothers. After the incident her mother is committed to a mental hospital. Niamh’s neighbors, Mr. and Mrs. Schatzman, tell her that her sister Maisie died in the hospital. They take Niamh to the Children’s Aid Society, and the agency sends Niamh out to the Midwest on an “orphan train.” On the train, Niamh befriends Dutchy, a twelve-year-old boy, and takes care of Carmine, a toddler. Just before Dutchy goes home with a farmer in Minneapolis, Minnesota, he and Niamh promise to find each other again someday.
In Albans, Minnesota, Niamh is taken home by Lois and Raymond Byrne. Mr. and Mrs. Byrne change her name to “Dorothy.” The Byrnes neglect and deprive Niamh, all the while exploiting her for free labor in their ladies’ garment business. After the stock market plummets, the Byrnes request to have “Dorothy” relocated. Mr. Sorenson, a Children’s Aid worker, takes Niamh to the home of the Grotes, a poor rural family with four children. Niamh hates the squalor and neglect at Wilma and Gerald Grotes’ household. One night, Mr. Grote sexually abuses Niamh. After Mrs. Grote finds them, she and Mr. Grote kick Niamh out into the cold winter night. Niamh walks to the local schoolhouse and sleeps on the porch. The next day, her beloved teacher, Miss Larsen, agrees to take care of Niamh for a while.
In between segments of Niamh’s story, the novel returns to the present day. When Molly first begins helping Vivian, she is annoyed by the stories Vivian tells about each item in her attic. She assumes that Vivian is a wealthy old lady who has had few problems. When Molly’s history teacher assigns her a project that requires her to interview an older person about their life’s “portages,” or journeys, Molly asks Vivian, who agrees.
As Vivian delves deeper into her life story, Molly realizes the parallels between Vivian’s life and her own. She also begins to see the attic project in a new light. Despite Jack and Terry’s concerns that Molly isn’t making any progress, Molly realizes the goal of cleaning out the attic is to give Vivian the opportunity to review her past, rather than to actually get rid of things. Molly grows fond of Vivian and becomes defensive of their friendship. The situation at Molly’s foster home continues to get worse, as her arguments with Dina escalate. One day, Molly decides to do some research about Vivian’s family history. As she looks through newspaper and record archives, Molly discovers that Vivian’s sister Maisie didn’t actually die in the fire. Rather, she was adopted by Vivian’s neighbors, the Schatzmans, grew old, and died just the year before. Molly grapples with the question of whether or not to reveal her discovery to Vivian.
The novel returns to the story of Niamh’s life. After a while, Miss Larsen’s kind landlady, Mrs. Murphy, arranges for Niamh to be adopted by Mr. Nielsen and Mrs. Nielsen, an affluent local couple whose daughter died a few years before. There Niamh finally has a safe, comfortable home. She agrees to take on the name of the Nielsens’ late daughter, Vivian, even though she finds it impossible to view the Nielsens as her parents. Over time, she tries to assimilate to the Nielsens’ way of life. Vivian’s only link to her past is the claddagh cross her Gram gave her before sending her family off to America. As a teenager, Vivian is well behaved, hardworking, and reluctant to get close to others.
In the present day, Molly finishes her community service hours. Dina and Molly get into a serious argument one evening, when Dina finds a copy of Anne of Green Gables – a gift from Vivian – in Molly’s room. Assuming it was stolen, Dina kicks Molly out. Molly escapes to Vivian’s house. That night, she tells Vivian the full story of her life. She tells Vivian the truth about her community service sentence and her discovery about Maisie. Vivian is startled by the news about Maisie, but she isn’t angry about Molly’s lie.
As the night goes on, Vivian tells Molly the rest of her life story. At eighteen, she went with some friends on a trip to Minneapolis. There, in the lobby of a hotel, she ran into a handsome man who turned out to be Dutchy. The two reconnected, fell in love, and soon got married. With Dutchy, Vivian again felt a sense of belonging and self-acceptance. After a couple of happy years together, they were torn apart when Dutchy was drafted during World War II. Dutchy died in battle, leaving Vivian alone and pregnant. Grief-stricken, Vivian gave away her baby daughter, determined never again to love someone so deeply that losing them would destroy her. She remarried a few years later to Jim Daly, Dutchy’s former shipmate. She and Jim had a harmonious but dispassionate marriage. Vivian kept her baby a secret, and had no more children.
In the present day, Vivian invites Molly to live with her. As her relationship with Vivian grows, Molly also deepens her relationship with Jack. At school, Molly is nominated for an award for her portaging project. With Molly’s support, Vivian decides to get a computer and reconnect with people from her past, particularly from the orphan train. After some time, Vivian asks Molly to help her find her daughter, and Molly helps Vivian sign up with an adoption registry. They find her daughter, Sarah Dunnell, who immediately arranges a visit to meet Vivian. As Molly helps Vivian prepare for Sarah’s visit, she is filled with a sense of peace and resolution. The novel ends just after Vivian and Sarah make eye contact outside of Vivian’s house.