Christmas, 1940. With Europe apparently on the brink of war, John Cabal is pessimistic about the chances for human progress. His friend 'Pippa' Passworthy is more positive - doubtful that war will come, and arguing that, in any case, war can be a force for progress. As Passworthy makes his goodbyes, however, the news comes through that the country is mobilising for war. Shortly after, Everytown is the victim of an air raid.

As war continues, Cabal, now a pilot, shoots down an enemy plane. As Cabal tends to the wounded pilot, the man tells him that he has released a deadly gas. Cabal struggles to equip them both with gas masks, but when a young girl comes by, the man insists that she takes his mask. Reluctantly, Cabal abandons the man to his fate.

1966, and the war continues to rage. The world is in the grip of a virulent plague, the 'Wandering Sickness'. The remaining inhabitants of the ruined Everytown are ruled by the warlike Boss, who demands that all sufferers from the sickness are shot to prevent contagion; in this way, the disease is eventually contained. The Boss continues to lead attacks on neighbouring communities, and dreams of a return to domination of the skies. But despite the best efforts of the mechanic Gordon, flight seems a lost science, until the arrival of a black-clad stranger in an aeroplane, who identifies himself as John Cabal, representative of Wings Over the World, an organisation striving to restore civilisation through the establishment of a world government.

Cabal renews contact with his old friend Dr Harding, and explains his mission. But he is arrested by the Boss, who proposes a deal if Cabal supplies him with fuel for his redundant planes. When Cabal refuses, the Boss imprisons him. Gordon, using Cabal's plane, makes his way to the headquarters of Wings Over the World, and a squadron is despatched, which rains down a 'gas of peace' over Everytown, putting all of its inhabitants to sleep.

Under Cabal's leadership, the rebuilding of civilisation begins, and mankind enters a new phase of technological and social development. By 2036, the new underground city of Everytown is complete. But its citizens do not all blindly accept the vision of progress that is being fed them, and one, an artist and sculptor, Theotocopulos, vows to oppose the relentless advance. Oswald Cabal, grandson of John and President of the Council, has proposed the next stage of scientific advance - a 'space gun' to begin the exploration of the heavens, starting with an orbit of the moon. The craft lacks only a crew for the expedition to begin.

Maurice, son of Cabal's colleague Raymond Passworthy, and Cabal's own daughter Catherine volunteer. But as the preparations are being made, Theotocopulos makes an appeal to the citizens of Everytown to prevent the launch. As the people march on the gun, the Council accelerated its preparations, and despite the pleas of Maurice's father, the crew are dispatched, and the gun is fired just before the mob can reach it. As the rocket makes its way into space, Cabal expresses his vision for mankind's future.