After the battle of Worcester at the end of the Civil War, the main aim of Oliver Cromwell's Commonwealth is to capture Charles Stuart. The future king's escape depends on the intrepid Earl of Dawlish, who as the Moonraker has already spirited away many Royalists. Dawlish travels to the Windwhistle Inn on the south coast to prepare the escape, where he meets Anne Wyndham, the fiancée of a top Roundhead colonel.

Following a group of five very different student nurses during their first year of training at an NHS hospital in London called St. Augustine’s Hospital (filmed at Guy's Hospital), where they live in a dormitory. Susan (Belinda Lee) is reliable and sensible; Pat (Delphi Lawrence) is flighty and open; Maureen (Adrienne Corri) is Irish and loud; Ann (Henryetta Edwards) is a typical public school girl; and Liz (Barbara Archer) comes from a typical working class background. As they get to know each other, they bond in spite of their differences.

An apartment handyman is unusually attached to a pair of boilers he names "Mavis" and "Ethel."