Stuck at her gran's house all summer with nothing to do, fifteen-year-old Rosie goes searching through some old junk and comes across a mysterious suitcase. It's full of vintage-style clothes, but when Rosie tries them on she finds herself suddenly flung back into the same house in war-torn London. With no idea of how she got there or how she can get back, she is soon caught up in a whirl of rationing, factory work, and dances, but comes crashing back to reality when she realises that if she can't find her way home, she may never be born at all.