In Edwardian England a vow of friendship is a thing of innocence. Even when tested by the passionate militancy of the suffragette movement or the rigorous demands of the Season, the bonds between Rory, Eleanor, Jenny and Francesca hold fast. But nothing can withstand the unprecedented onslaught of the First World War — and as the best of an entire generation is extinguished on the battlefields of Europe, a schoolgirl pledge, too, lies broken...

Cassie is nothing if not organised. A successful journalist, she's ticked almost all the boxes: attentive boyfriend, own flat, good job, great friends... it's all fallen into place. In theory, at least. There's one part of Cassie's life, however, which is anything but organised, and that's her love for the Darling family. As the only child of ambitious parents, Cassie spent her childhood abandoned to the somewhat peremptory care of a series of nannies until one day, peeping over the garden wall, she met her nextdoor neighbours: Fritz and Ben, the boys who became her inseparable childhood friends, Gudrun, their father, and Phoebe Darling, the woman who took Cassie in and transformed her life. But now Phoebe is ill, and when she summons Cassie to ask of her the only favour she's ever requested, Cassie knows she can't say no. But what Phoebe asks is an impossibility: concerned about what will happen to Fritz and Ben after her death, she wants to see them safely married off. Yet entertaining as they were as children, they're terrible as adults. They're utterly charming, ridiculously sexy and completely irresistible, but they're also totally unemployable, hopelessly messy and irretrieva.