The film begins by describing Britain's nuclear deterrence policy of threatening would-be aggressors with devastation from the
Royal Air Force's nuclear-armed
V bombers. Due to the number of
V bomber bases (particularly in a crisis situation that would see them dispersed throughout Britain), as well as
major civilian targets in cities, Britain is described as having more potential nuclear weapon targets by area than any other country. On 15 September,
American forces in
South Vietnam are authorised to use
tactical nuclear weapons in response to an ongoing
Chinese invasion. The
Soviet Union and
East Germany threaten to invade
West Berlin if America does not change course. The next day, the British government declares a state of emergency and transfers responsibility for Britain's day-to-day running to a body of
regional commissioners. The first task of newly established emergency committees is the mass evacuation of children, mothers, and the infirm to various safe areas including
Kent. Under threat of imprisonment, homeowners accommodate the evacuees, while unoccupied properties are requisitioned by the government. Rationing is implemented, booklets on how to prepare for nuclear attack are distributed, and
emergency sirens are tested, with these being estimated to provide around three minutes' warning until impact, or under 30 seconds in the case of
submarine attack. There are no government-built shelters and efforts to build private ones are soon frustrated by a shortage of construction supplies. On 18 September the Soviets and East Germans invade West Berlin as previously threatened. NATO launches a counterattack, which is quickly overrun, resulting in the use of American
tactical nuclear weapons. The Soviets immediately launch their own nuclear weapons at strategic targets, as their above-ground
liquid-fuelled missiles are highly vulnerable to a NATO first strike. In Kent a one-
megaton warhead that overshoots
RAF Manston explodes in an
air burst six miles from
Canterbury, causing the city to be struck by the intense heat given off by the blast. At one house a defence worker and a boy in the yard are struck by the heat wave, causing their eyeballs to melt. Furniture inside the house catches fire, causing those inside to panic as they attempt to put the flames out. Twelve seconds later the building is destroyed by the incoming
shockwave. At another house a boy suffers
flash blindness as a consequence of looking directly at an explosion 27 miles away; his father carries him inside and hides with the rest of his family under a table as the house is shaken by the distant shockwaves of successive explosions. In
Rochester, an airburst causes a
firestorm, which sets the town ablaze. Meanwhile British V bombers enter Soviet airspace to
inflict similar devastation. The attack overwhelms Kent's emergency services, with each surviving doctor being faced with at least 350 casualties. The worst-affected victims are left to die alone or shot by police as a form of
mercy killing. Cases of
PTSD occur among the survivors of the attacks. Bodies are disposed of by being burned; to prevent relatives from interfering, destroyed areas are sealed off, and police are
routinely armed.
Radiation sickness is rampant and essential supplies and utilities are non-existent or severely limited. The majority of Britain's remaining food supplies are reserved for those maintaining law and order, causing riots to break out over access to resources. The riots soon turn into armed skirmishes between the authorities and desperate civilians; the latter are shown seizing a truck carrying a shipment of weapons and a food
warehouse. Elsewhere individuals convicted of causing civil disturbance or obstructing government officers are executed by police
firing squads, with the father of the blinded boy from earlier in the film among those shot. Due to food shortages,
scurvy emerges as a consequence of a lack of easily available
vitamin C. On
Christmas Day in a
Dover refugee facility children orphaned in the attack are asked what they want to be when they grow up; they either "don't want to be nothing" or simply remain silent. Another child is described as having only seven bedridden years to live before dying from a chronic illness resembling
leukaemia, and a pregnant woman who was exposed to radiation is unsure if she will suffer
stillbirth. In closing, the real-world press is described as saying nothing about the dangers of nuclear weaponry. Over the closing credits, one can hear a damaged recording of the
Christmas hymn Silent Night (Mohr and Gruber, 1818). ==Style==