Adeline, a young girl, lives with her abusive mother and kind father in 1900's Boston. The mother always goes to the bar and cheats on her husband. Meanwhile, her husband has sacrificed so much for his wife. He gave up his love for the sea to work as a cobbler to support the family. Unfortunately, the chemicals from his job made him very sick, and he died. After her father's death, Adeline refuses to speak and only communicates through writing. Meanwhile, her mom, as a widow, needs work. She decides to work for a lighthouse as a maid with Adeline. When they arrive, they meet three couples who live at the lighthouse. The mom instantly sets her sights on Rowan, a man married to Julia. The mom and Rowan immediately begin to have an affair which Adeline finds out from a book the mom keeps. In the book, the mom and Rowan write about their sexual exploits. Meanwhile, Julia is unaware of her husband's infedelty. On the island, Julia and Adeline become very close. They cook, clean, and work together. One day, Julia finds the book and is heartbroken. Julia doesn't know what to do and doesn't mention the infidelity to the husband. When the mom finds the book gone, she blames Adeline and takes her out of school. Julia begins to suffer more grievances as Rowan starts beating up Julia. None of the other people stop him and Adeline realizes that Julia has to leave the island. Adeline tells Julia to row off the island in the middle of the night. Adeline explains that everyone will think Julia committed suicide, and they will blame the mom and Rowan. Julia does as told, but the plan appears to have backfired. Nobody mentions Julia's disappearance. Additionally, the mom marries Rowan, moves into his house, and makes Adeline do all the cleaning. However, this all changes when a reporter comes to the island. He's interested in why a wife would kill herself and believes there was foul play. He asks Adeline, and Adeline reveals that Julia is alive. Since Rowan married another wife while Julia was alive, he technically committed polygamy. Rowan is sent to prison for two years, and the mom is fired. The mom and Adeline return to Boston, and the mom wants Adeline work for a bar. However, Adeline has other plans. As soon as they leave the train, Adeline runs into the crowd to find Julia and live with her. She has a house and plans to take care of as her daughter and send her to school