It won the 2007 Bolton Children's Book Award, the 2008 Manchester Book Award and the 2007 Red House Children's Book Award for Older Readers, as well as being longlisted for the Carnegie Medal. It was also one of the books picked for the Richard & Judy Children's Book Club.
The main character is Lauren Matthews, who lives in London with her adoptive parents and adoptive brother, Rory. Lauren is doing an essay for homework entitled Who am I?, in which she has to write about her personality and her life. Eager to find out about her past, Lauren goes on Missing-Children.com, and finds an American girl of her age named Martha Lauren Purditt, who went missing less than two months before Lauren was adopted.
After comparing the photograph of Martha with a photograph of Lauren as a toddler, Lauren finds that she and Martha look alike. Lauren's friend James 'Jam' Caldwell comes round, and compares Lauren's face to the age-progressed photograph of Martha. They find that the two girls look alike. Lauren thinks she may be Martha, and finds out information about her adoption is in her adoptive mother's diaries. Whilst Lauren's mother is visiting Jam's mother Carla, Lauren finds her mother's diaries in the attic, and discovers she was adopted from Marchfield Adoption Agency in Vermont, USA. After persuading her family to go on a holiday to a theme park in America, the family go to America (albeit leaving Lauren's adoptive father behind, and taking Jam in his place). While Lauren's mother and Rory are waiting to change planes, Lauren and Jam sneak off and get a plane to Burlington.
Once the plane lands, Lauren and Jam get a bus to Marchfield, where Lauren has a meeting with Taylor Tarsen, the owner of the agency. He refuses to show Lauren her adoption file, but when Lauren mentions Sonia Holtwood, a woman from her mother's diaries, Taylor tells Lauren she was looked after by Sonia before her adoption, and gives her $150 so she and Jam can stay in a motel. Jam informs Lauren that he found out where Lauren's adoption file is, and the two stay in a motel for the night.
That night, Lauren and Jam break into Marchfield and find Lauren's adoption file, but all that is in it is an address on a scrap of paper. Unfazed, Lauren and Jam go to an 24-hour taxi firm and get a taxi to the address. When they arrive at what they believe to be Sonia Holtwood's flat, they find that a young Spanish woman now lives there. However, they meet an old woman named Bettina, who used to babysit Lauren when she lived in the flat with Sonia.
Lauren and Jam set out to find Sonia but end up cold and worried so when a "Police officer" comes up to Lauren and offers to take them to their destination Lauren accepts. After a brief discussion with Jam he accepts and he goes with her. The officer tells them who she really is and they find out she is Sonia Holtwood and she is trying to kidnap them. She gives them orange juice which is drugged so they both fall into a deep sleep and wake up hours later to find they are still in the car. Lauren pleads with Sonia to let them out and she does: in the middle of nowhere, twenty miles from the nearest place with a name. So Lauren and Jam start walking through the woods where they have an argument. Jam storms off so Lauren just lies down in the snow. She hears voices then goes back to sleep. The next day she wakes up in a log cabin. She sees Jam and asks him what has happend. He says they were rescued by a man called Glane who took them to his log cabin. He then takes them to a motel for them to stay at because he was going home to Boston. Lauren goes on the internet to find out more about Martha Lauren Pruditt. Her parents were Annie and Sam Pruditt who lived in Evanport. Lauren decides she will hitch hike to get there but Glane won't hear of it so he takes them there hiself. On the way Lauren is worrying about how she looks but Jam says she looks beautiful and he wants to ask her something
At the house, lAuren is met by a girl aged thirteen, called Shelby who dosen't believe Lauren. Then a lady comes out and asks who Lauren is. Lauren repiles she is Marthea. After a lot of explaining, Lauren meets the other realatives, her real father and a sister Rory's age