Sixteen-year-old Nigerian refugee Little Bee has spent the past two years in an immigration detention center in Essex, England. In 2007, Little Bee is released from the detention center with three other women, none of whom have their papers or documentation granting them asylum status. However, Little Bee has a driver’s license and business card belonging to Andrew O’Rourke, a white man she met two years before on a beach in Nigeria. She calls Andrew, who seems angry and hostile, and tells him that she is coming to his house because she doesn’t know anyone else in the country, regardless of whether he wants her to or not. Little Bee and the three other women go outside to wait for a taxi.
Ten days later, Andrew’s wife, Sarah, a magazine editor, and four-year-old son Charlie—who wears his Batman costume at all hours and will only respond to “Batman”—are preparing to attend Andrew’s funeral. Five days after Little Bee contacted Andrew and told him she was coming, Andrew hanged himself. Little Bee arrives on the day of the funeral and attends with Sarah and Charlie, forming an instant bond with Charlie. Sarah briefly recalls her first encounter with Little Bee on the Nigerian beach, and notes that her only memento from that day is the missing middle finger of her left hand.
Little Bee recalls her escape from Nigeria, during which she stowed away on a cargo ship carrying tea. On the voyage, she has nightmares about the horrors she has seen, and after British immigration authorities lock her in the detention center she continues to suffer traumatic nightmares each night. She spends her first six months in detention fantasizing about different ways to kill herself, but she eventually begins to feel a sense of hope and teaches herself to speak English like the British.
Ending her recollection, Little Bee and the other women wait until a taxi comes to meet them, but the driver despises refugees and leaves them behind with no transportation. The four women begin walking down the highway until they meet a farmer named Mr. Ayres who gives them shelter in one of his farmhouses, even though he could face criminal penalties for doing so. That evening, with shelter and food, one of the other three women, Yevette, reveals that she had sex with one of the detention center officers in exchange for her release, but the man wanted to release several women at once so it would look like a clerical error. However, without paperwork, Little Bee and the others realize they are now illegal immigrants, even though they had wanted to enter the country legally. In the middle of the night, one of the women, who was severely traumatized, hangs herself. Little Bee wakes to find her body and realizes that there will inevitably be an investigation and policemen, so she leaves on foot in the middle of the night to find Andrew’s house.
Resuming Sarah’s narrative, after the funeral, she, Charlie, and Little Bee return to her home and Little Bee recounts some of what happened to her on the beach and in the years since then.
Right before she meets Andrew and Sarah on the Nigerian beach, Little Bee and her sister Nkiruka see mercenaries for the oil companies slaughter their entire village so they can take their oil-rich land. Little Bee and Nkiruka flee to the jungle and hide until they hear hunters and dogs pursuing them. When Little Bee and Nkiruka see Sarah and Andrew on the beach, on vacation, they run to them and beg Andrew and Sarah to take them back to their hotel with them to hide. The hunters arrive to take Little Bee and Nkiruka, but the leader states that if Andrew cuts off his own middle finger, he’ll let the girls live. Andrew cannot bring himself to do it, so Sarah takes the hunter’s machete and cuts her own finger off instead. The hunter announces that Little Bee will live, but Nkiruka will die because of Andrew’s failure, and takes the two girls away.
In Sarah’s living room, Little Bee falls asleep for the night and Sarah calls her married lover, Lawrence, to ask what she should do. Lawrence is horrified that Little Bee is in Sarah’s home, believing she is dangerous, and tells Sarah to turn her in to the police.
The next morning, Sarah asks Little Bee to continue her story. After Sarah and Andrew return to the hotel, the hunters take Little Bee and Nkiruka down the beach, where Little Bee hides under an overturned boat while the mercenaries rape, torture, and kill Nkiruka, cannibalizing her body. During the night, Little Bee slips away and goes back to the place where she met Andrew and Sarah and finds Andrew’s wallet in the sand, with a business card and driver’s license. Little Bee continues her flight until she finds a trading port, where she manages to stow away aboard a cargo ship bound for England.
When Little Bee concludes her story, Sarah thinks back to the events that brought her and Andrew to that beach in Nigeria: in 2005, Andrew and Sarah’s marriage is lifeless and tense, so she begins having an affair with Lawrence, who works for the government’s Home Office, which governs immigration. After six months of sleeping together, Andrew discovers Sarah’s affair, which deeply wounds him. To make amends, Sarah convinces Andrew to take a holiday with her to Nigeria so they can try to fix their marriage.
In the present, Lawrence arrives at Sarah’s house unannounced, intending to stay for several days after he lied to his wife that he is on a business trip. Sarah does not want him to be there, since she is trying to figure out what to do with Little Bee, but after a brief argument decides that she wants Lawrence to stay. The next day, while Sarah is asleep, Lawrence and Little Bee have an argument—Lawrence threatens to call the police on Little Bee, but Little Bee warns him that if he does, she’ll tell his wife about the affair and turn Sarah against him as well, effectively ruining his life. After establishing their stalemate, Little Bee confesses that she did not actually arrive on the day of Andrew’s funeral, but several days before Andrew died. Little Bee had hid in the bushes in their garden until Andrew was alone. When she approached him, Andrew thought she was a guilt-induced hallucination and hanged himself. Little Bee tried to stop him but couldn’t, and thought that she could save him by calling the police, but that would result in her own arrest and deportation. So, she let him die. The confession horrifies Lawrence, but he knows they both have much to lose, and they’ll keep each other’s secrets.
The next day, Sarah, Lawrence, Charlie, and Little Bee take a day-trip to South Bank in London. While Little Bee looks at the throngs of people in the city, she considers simply disappearing amongst them and takes her first steps until she realizes she cannot bear to leave Charlie behind, especially since she knows that Lawrence does not love him. Little Bee plays with Charlie next to the river, and Charlie reveals that he can’t take his Batman costume off because he thinks that if he stops being Batman, his father will be truly dead. Little Bee assures him that this isn’t true and reveals that her identity as Little Bee is a costume too. Charlie wants to know her real name, so Little Bee offers that if he’ll take off his Batman costume, she’ll tell him what her real name is, but Charlie refuses. While Lawrence plays with Charlie, Sarah tells Little Bee that she found thousands of pages of research in Andrew’s study about the Nigerian oil wars and the refugee crisis in England and thinks he was planning to write a book on it. Sarah wants to continue his work herself, and calls her boss to tell him that she is quitting her job.
In a moment while nobody is watching him, Charlie disappears, prompting a frantic search in which they all fear that Charlie fell in the river and drowned. As they search, Lawrence gives Little Bee his cell phone and tells her to call the police. She does so, but Lawrence finds Charlie before they arrive. However, when the police do arrive, one of them suspects Little Bee of being an illegal immigrant and arrests her. That night in prison, Sarah visits Little Bee and Little Bee confesses that she did not save Andrew from his death. Surprisingly, Sarah is not angry, but confesses that she feels as if she did not do enough to save him either.
The police deport Little Bee three days later, but after she is seated on a plane back to Nigeria, she discovers that Sarah and Charlie are on board as well. Sarah announces that Little Bee is her family now, and she is never going to stop trying to save her. Little Bee knows that since she witnessed the oil companies’ genocides, her own government will try to illegally kill her when she returns. To prevent this, Sarah stays by Little Bee’s side at all times, reasoning correctly that the Nigerian authorities would not dare commit such a heinous action in front of a British journalist. Sarah and Little Bee spend the next several weeks meeting survivors like Little Bee and recording their stories, and Sarah hopes that by publicizing what is happening in Nigeria, she might save Little Bee and other refugees’ lives.
Sarah and Little Bee risk taking a trip to the beach so that Little Bee can bid Nkiruka a proper farewell. As they stand on the beach together, Charlie plays with the Nigerian children in his Batman costume. However, three soldiers start coming up the beach; Sarah knows they are looking for Little Bee. Little Bee runs up the shore to hide, but when the soldiers are talking with Sarah, pointing their rifles at her, Charlie runs towards Little Bee. One of the soldiers shoot at Charlie but misses, and Little Bee runs towards him scoops him up in her arms, revealing herself. As Little Bee holds Charlie, she asks him to take off his Batman costume so he can play freely with the other children. She tells him her real name is Udo, and Charlie, emboldened by her courage, takes off his costume and runs to play with the other children in his own skin. Even as the soldiers reach Little Bee, she thinks the sight of Charlie playing freely and being himself is so beautiful that she cries tears of joy.
