One night in 1987 an abandoned baby girl is found in a cleaning cupboard at Heathrow airport. A year earlier, three girls, Martha, Clio and Jocasta had met by chance, at the start of a backpacking adventure: they travelled together briefly and then separated to go their different ways, swearing to meet again when they return home. But it would be a long time until they met again: not until Kate, the foundling, is a teenager, and the three women are all leading successful lives. Martha is a fiercely single, highly paid corporate lawyer, Clio a doctor, locked in an unhappy marriage to a surgeon, and Jocasta a reporter for a tabloid newspaper, in love with a charming commitment-phobe. Which of them is Kate's mother? Why was she desperate enough to do such a thing, and how did she survive it?