Kay Duffield's fiancee is about to leave the country, and her own duty with the WAAF is imminent when she becomes a bride. The precious few days she spends with her new husband are quickly forgotten once she starts work as a balloon operator, trained for the heavy work in order to release more men to fight. There she makes friends with shy Emily Bevan, who has left her parents' hill farm in Wales for the first time; down-to-earth Biddy Bachelor, fresh from the horrors of the Liverpool bombing, and spirited Jo Stewart, the rebel among them, whose disregard for authority looks set to land them all in trouble. The girls stay friends through good times and bad, through romantic encounters and, ultimately, tragedy.