Swastika Night takes place in a world where the Nazis and Empire of
Japan defeated their enemies and conquered the world (from a modern
perspective, the novel is an alternate history in which the Nazis won
World War II, though at the time of its writing the war had not broken
out and it was a work of speculative future fiction.) It follows the
protagonist Alfred, an Englishman in his 30s who works as a ground
mechanic for the German Empire in the Salisbury Aerodrome. Alfred
comes to Germany on a holy pilgrimage to see the holy sites of
Hitlerism, the religion in this Nazi-dominated world. These sites
include the holy forest and the sacred aeroplane in Munich with which
Hitler won the war by personally flying to Moscow, it is said. In this
world Hitler is seen as a seven foot tall, long blonde-haired,
blue-eyed man who was “exploded” from the head of God the
Thunderer and was a god in his own right. He is preached about by
"Knights" (a cross between the traditional, feudal knight and a
priest) who pass this job down from father to son.

When Alfred arrives at his Nazi friend Hermann's village, he meets the
Knight there, an old man by the name of Friedrich von Hess; Hermann
works on this Knight's land. The Knight reveals to Alfred about how
history was distorted by a man who even when confronted by the truth
proclaimed Hitler a god. The writing of this man's book caused the
Nazis to burn everything that contradicted the fact – even the book
itself – and also anything that revealed life before the empire or
during Hitler's life. An ancestor of von Hess wrote about the truth
and entrusted the secret to his descendants as he also obtained and
preserved a picture of Hitler and a young blonde woman that Alfred
originally mistakes for Hitler. This convinces the already sceptical
Alfred that Hitler was not a god when he sees that Hitler was a small,
brown-haired man with a paunch.

Alfred then vows to return women to how they should be as in the novel
they have become ugly things, with shaved heads and no self-respect,
used solely for reproduction and kept in a place called the women's
quarters from where they cannot escape and are seen as little more
than animals. He also vows that he shall teach what is in his book to
his fellow Englishmen and others so that eventually they can cause the
shattering of the German Empire as the belief that holds it together
falls apart. He presses that it must be an ideological, spiritual
rebellion as a violent rebellion would be crushed by the occupation
armies of the Germans. The reader may also realise that a violent
rebellion would also only adhere to the Hitlerian beliefs of violence
and strength.

Towards the end of the novel Alfred returns to Britain with the book,
where he starts teaching his son from it. A few weeks after finishing
the book Alfred, his son and Hermann (who followed Alfred to Britain)
are almost caught by Nazi soldiers. While Fred (Alfred's son) escapes
with the book, Hermann and Alfred are discovered, whereupon Hermann
charges the soldiers and is killed. After this happens the soldiers
try to discover the reason behind Hermann and Alfred being there, but
are unsuccessful. A soldier then kicks Hermann's corpse, causing
Alfred to fly into a rage and get beaten into unconsciousness; the
beating is so bad that Alfred wakes up in hospital two days later and
gets to talk to Fred one last time about continuing his work just
before he dies of his injuries.