A virulent flu bug is spreading through the country like wildfire. Abby Grant (Carolyn Seymour) and her husband David (Peter Bowles) are aware that the flu has reportedly claimed millions of people's lives in China, but they don't think that could happen in England. Abby becomes ill and takes to her bed. Meanwhile Jenny Richards (Lucy Fleming) learns from a doctor that this is no flu bug and that hundreds are now dying. Acting on his advice she flees London for the countryside. Abby wakes days later and fears that she may be the only one left alive...