War begins for the United Kingdom after a surprise aerial bombing of 20 cities, the first of many attacks. Young solicitor Peter Corbett, wife Joan, and their small three children leave Southampton after their house and Corbett's offices are damaged, friends are killed, and a cholera epidemic begins. They move aboard their small yacht, kept on the river Hamble, but as disease spreads and supplies diminish, flee the area. They sail to the Isle of Wight, but because of the fear of disease, other ports require them to provide a certificate of health or wait in quarantine; the Corbetts do not want to risk being bombed during the three weeks of quarantine.
