In 1998, the Richardson home catches fire. Arson is suspected, as there were multiple small fires.
The previous year, 1997, Elena Richardson rents her rental home across town to Mia Warren, an artist, and her teenage daughter, Pearl. Elena's younger son, Moody, who is Pearl's age, develops a crush on Pearl and becomes friends with her. Pearl meets his siblings Lexie, Trip, and Izzy. Pearl, who is used to a transient lifestyle in which her mother scrapes together money, is charmed by the Richardsons and their established home. She spends time every day at their home, develops a crush on Trip, and idolizes Lexie.
Mia works part-time at a Chinese restaurant and sells photographs through a dealer in New York. She becomes concerned about Pearl's idealization of the Richardsons. When Elena condescendingly offers her a job doing housekeeping for her family, she agrees only to keep an eye on Pearl. She meets Izzy, the black sheep of the family, and the two become close.
The Richardsons are invited to the birthday party of Mirabelle McCullough, the adopted daughter of Elena's friend. Mia realizes that the child is May Ling Chow, the daughter of Bebe Chow, Mia's co-worker at the restaurant, who gave up her child in the middle of a postpartum episode and economic hardship. Bebe has been looking for her child for over a year. Mia informs Bebe, though the McCulloughs refuse to let her see Mirabelle. Bebe is despondent as she has no money for lawyers. Mia advises her to get the local news involved. The scandal results in Bebe getting visitation rights and help from a lawyer pro bono.
Elena discovers that Bebe learned of her child's whereabouts through Mia. Angry on behalf of her friend, she investigates Mia's past. She tracks down Mia's parents and learns that Pearl was conceived by Mia for a wealthy New York couple who were unable to have children of their own. Mia could not face the idea of giving up her child. She told the couple that she miscarried and ran away with Pearl; Mia's parents hadn't heard from her since.
Lexie gets pregnant and asks Pearl to come with her to get an abortion. Afraid of being discovered, Lexie uses Pearl's name at the clinic. Pearl and Trip begin to have sex, which they keep a secret from everyone. When Moody discovers what's going on, he and Pearl stop speaking. Elena investigates a suspicion that Bebe had an abortion and, to her shock, discovers Pearl is listed as having had one. She confronts Moody about being the father, but he tells her she is accusing the wrong son.
Bebe Chow loses her case and Mia comforts her. Elena tells Mia she knows about Pearl and that she must move out. Pearl is reluctant to go, but Mia explains about her biological father and she accepts. Izzy realizes that Moody, Lexie, and Trip have all used Pearl in their own way and becomes angry at them. Choosing a moment when they are all out of the house, she starts small fires on everyone's beds, not realizing that her mother is still in the house. Elena manages to escape the fire unharmed. After the fire, the Richardsons go to the rental home, now vacated by the Warrens, where they find that Mia has left them with photographs that have personal significance to each of them.
Bebe Chow, using Mia's words as inspiration, sneaks into the McCulloughs' home and kidnaps her daughter, flying with her to Canton. The McCulloughs unsuccessfully spend thousands of dollars searching for them. Eventually, they are approved to adopt a baby from China. Mia and Pearl hit the road, planning to reconnect with Mia's family and Pearl's father. Izzy runs away to Pittsburgh with the name of Mia's parents, promising herself that if she is caught and returned, she will continue to run away until she is never forced to come back again. Elena realizes that her greatest fear, losing Izzy, has come true, and vows to spend the rest of her life looking for her daughter.
