Laura Williams tolerates her family’s move to London, mainly because it allows her a sense of freedom that she did not have in suburban America. In London, she can take a bus or train anywhere she wants to go and does not have to rely on her parents or a friend with a car. Unlike her classmates at the prestigious international school she attends, Laura is not interested in foreign affairs or politics. She is only interested in boys and getting a date to the upcoming Thanksgiving dance.
Things change when a bomb in the London Underground kills Laura’s younger brother, Billy, on his way to school. Laura can’t accept that this was a random terror attack. She believes someone targeted her brother. Laura begins to question all of her friends at school to learn if any of them have ties to terrorists.
She questions her friend Jimmy at lunch. He claims to be American. At first he is happy to tell her about his family’s heritage, but when she seems to doubt his statement that he is only distantly Japanese, he becomes perturbed. Laura asks to see Jimmy’s passport as proof he is really American, and Jimmy grows angry. Her best friend, Consuela — Con, for short — tries to convince Laura that she is on the wrong track because no one at school would want to kill Billy.
Her friend, Mohammed, also counsels her to stop questioning people and looking for answers to Billy’s death. It can only lead to trouble. Laura remembers he is from Palestine, a land with a lot of terrorists. She asks to see his passport, but Mohammed admits he is in the country illegally. He does not have papers. His family, like many others at the school, pay to have the school officials overlook the fact that they do not have the proper papers. Mohammed tries to get Laura to think about what her faith has taught her about life after death. Sitting in class, Laura realizes that no one, especially not God, has the answers she desperately wants.
After Thanksgiving, Jehran, one of the coolest, wealthiest and prettiest girls in school, announces that she is going to have an American-type sleepover at her house. She will need guidance from all her American girlfriends about how a sleepover works. Jehran makes a point of asking Laura to the party, insisting Laura ask her parents if she can attend. Jehran wants to have this party to help lift Laura’s spirits.
An iron fence surrounds Jehran’s house. Guards with guns patrol the hallways. Laura is saddened to learn that Jehran’s parents are dead. She lives with her brother, who is in his 30s.
While the other girls are in Jehran’s dressing room trying her perfumes, Jehran and Laura talk. Jehran asks Laura for help. Her brother is going to force her to marry a much older man in order to secure their safety back in their homeland. She will be a virtual slave to this man. She begs Laura to give her Billy’s passport. Jehran is very small with dark hair. Even Laura’s mother once remarked that she resembled Billy. At first, Laura refuses, but Jehran continues to plead for her help to escape to America with Billy’s passport.
The first day back to school after the sleepover, Jehran gives Laura an envelope with hundreds of English pounds. She wants Laura to buy her a plane ticket to New York. Once she arrives there, she will blend in with the other immigrants, and her brother will never find her. Because Billy’s passport labels her as an 11-year-old, Jehran will not be able to travel alone. She must have a guardian.
Jehran asks Laura to buy a plane ticket for herself as well because Laura is 16. She can act as “Billy’s” guardian. Laura will only have to fly to New York. Then she can turn right around and fly home without Jehran.
Laura explains that she can’t be gone for 24 hours, as her parents would call the police looking for her. Jehran comes up with a plan to pretend they are going with the Walking Club’s weekend trip to Edinburgh. Laura finally agrees to help.
Laura’s other friends at school begin to suspect something is wrong with her, and some are suspicious of Jehran’s motives. Jehran’s prejudice against Americans is well known. One friend, Jimmy, secretly follows Laura as she makes her way to a tourist agency in a seedy part of the city.
When he learns that Laura has bought two tickets to New York over the holiday, and one is for her dead brother, he thinks she has lost her mind. Unsure of what to do, he does not tell anyone, but continues to keep his eye on Laura. Her friend, Mohammed, is suspicious of Jehran’s sudden friendship with Laura, but when he tries to ask his father about Jehran’s family, he is ordered to stay away from them.
Laura’s parents agree to let her go to Edinburgh on the school trip. She meets Jehran at the train station and gives her a jacket and ball cap that belonged to her brother. They also cut off Jehran’s long hair. When Laura tries to carry Jehran’s leather bag, Jehran becomes belligerent. Only she can carry the bag.
Laura’s friend Con calls the Williams’ house before going to Edinburgh and learns that the Williams think Laura is going with her. Con talks to Mohammed and Jimmy, and the three put together what they have seen over the past few weeks. They realize what Laura and Jehran are planning to do. They fear Jehran is the terrorist who killed Billy just so she could use his passport. They decide to call the authorities.
Laura battles her fear while going through the airport, but notices that Jehran does not seem afraid. She seems to be amused at what they are doing. When Laura suggests they stop to get a hamburger before the flight, Jehran refuses. She loathes hamburgers. Laura tells her that if she is going to pass as an American boy, she had better not be so picky about her food. Jehran apologizes for being rude and says she is only nervous about the trip, but Laura knows she is lying.
After the final checkpoint before reaching the gate, Laura tells Jehran that she is not going to get on the plane. She is going to go home. She fears her parents will find out she is not on the trip and will worry. When Jehran pleads with her, saying that she has spent weeks on this plan, Laura’s skin crawls. Jehran could only have spent weeks on this plan if she knew Billy was going to die.
Jehran neither confirms nor denies Laura’s accusation that she had something to do with Billy’s death. Jehran clutches her leather bag to her side and acts like there is a bomb inside. Laura grabs it from her and accuses her again of killing Billy. As the people around them hear her words, they begin to suspect there is a bomb in the bag and start to run away. Jehran knows she cannot get on the plane now, so she turns and tries to blend in with the fleeing crowd. Airport security, alerted by Laura’s friends, arrives. They have Laura carefully put down the bag and then they apprehend Jehran.
Jehran insists that she had nothing to do with Billy’s death, but the authorities take her into custody. The leather bag only contained money, not a bomb. In the end, as Jehran’s brother and his armed guards have abandoned their house, and nothing could prove Jehran’s guilt; she is put into foster care. She walks away from the home several months later and is never heard from again.
Laura and her parents return to America. Although they pick up the pieces of their lives, none of them, especially Laura, ever truly get over Billy’s death. But Laura is left with the knowledge that she was loved by him and by her friends back in London.