*The article contains spoilers for "The Odyssey"

Christopher Nolan is one of the most fascinating filmmakers of our time.I mean that in both bad and good ways.

He has a rare ability to make movies that are simultaneously crowd-pleasing cinema fare and thought-provoking feats of storytelling that explore the most challenging aspects of the human condition.

He's also prone to getting so wrapped up in the exploration of ideas and intricate narrative structuring that he neglects to give his characters any interiority, especially if they happen to be women.

That's why the same filmmaker who made such endlessly rewatchable films as Inception, The Dark Knight and The Prestige also made such confounding and frustrating, if at times also captivating, films as Dunkirk and Tenet.

Nonetheless, a new Nolan film is always an event and The Odyssey is no exception.

Before it was released, it became the subject of heated debate and culture war trolling that will continue as it dominates the box office.

But my interest was always in how Nolan would use an ancient text to explore the themes that have been the staples of his oeuvre: memory, guilt, identity, sacrifice and the consequences of human ambition.

Having watched the film, I can say that Nolan's adaptation of The Odyssey might be the purest expression yet of his recurring obsessions.

He's made a three-hour swords-and-sandals epic filled with monsters, gods, witches, warriors and battles but beneath the surface of the Aegean seas is a film that uses ancient mythology to deliver a timely and timeless message.

The Odyssey is about the tendency of right-wing political movements to blame foreigners for the decay of their societies when the source of that decay is coming from within.

The threat, throughout the film, comes from the sea.We repeatedly hear about "the people from the sea" causing trouble across the region.They are spoken about as an external threat, a destabilising force arriving from elsewhere.But eventually we understand that the people from the sea are actually Odysseus and the Greek soldiers who went to fight the Trojan War themselves.

The people who claim to be defending civilisation are also responsible for violently disrupting it.This is where the film's ancient setting begins to feel remarkably modern.

In Britain, refugees who arrive by boat have often been reduced to the dehumanising phrase "boat people", becoming a convenient symbol for a society's anxieties about immigration and national decline.The stranger becomes the threat.The foreigner becomes the explanation for everything that has gone wrong.

But The Odyssey turns the logic inside out.The danger doesn't come from somewhere else.

The supposedly civilised Greeks have invaded Troy, destroyed a city through deception and violence and then returned home carrying the consequences of their actions with them.Odysseus is the defender of civilisation and one of the men responsible for destabilising it.

There is an additional layer to this in the film's treatment of Zeus's Law, or xenia, the ancient Greek principle of hospitality toward strangers and guests.The word shares its Greek root with xenos, meaning a stranger or foreigner, from which we also get the modern word "xenophobia".

The connection creates a fascinating tension at the heart of the film.Xenia demands hospitality towards the stranger.Xenophobia turns the stranger into an object of fear.The question is what happens when a society abandons the former and embraces the latter.

Nolan has always been fascinated by the consequences of actions that initially appear heroic or necessary.He is less interested in the achievement of greatness than in what that greatness ultimately costs.

What does it cost Bruce Wayne to become Batman?What does it cost Alfred Borden and Robert Angier to pursue the perfect illusion in The Prestige?What does it cost J Robert Oppenheimer to become the so-called "father of the atomic bomb"?In each case, the achievement is only the beginning of the story.The real drama comes afterwards.

Odysseus is the perfect Nolan protagonist because he's achieved something extraordinary and is then forced to live with the consequences.His idea for the Trojan Horse helps the Greeks win the war but the victory is achieved through a violation of the customs of civility that had governed the world before.The deception leads to untold bloodshed.

Odysseus comes to believe that this one act has planted a seed that will eventually lead to the collapse of civilisation under Zeus's law.

The great achievement has become a source of guilt."Why don't you want to go home?" Athena asks him.It's one of the most important questions in the film because it reveals that the monsters and obstacles Odysseus encounters on his journey are not necessarily the main reason he cannot return to Ithaca.The real obstacle is himself.

This is where The Odyssey becomes a story about Post-Traumatic Stress Disorder and the way war changes people irrevocably.Odysseus spends 20 years away from his wife and son but when he finally returns, he discovers that the world he left no longer exists."That world is gone!" Penelope tells Telemachus.

Odysseus tells Penelope that the husband she knew is gone too.Perhaps he died in the fires of Troy.

The man who returns home is not the man who left.That's a very Nolan idea.The filmmaker is obsessed with stories of men who desperately want to return home to their families but can't.

Cobb wants to return to his children in Inception but he is psychologically trapped by his guilt over his wife Mal's death.Cooper spends Interstellar trying to get back to his daughter Murph, only to discover that time has made the home he left almost impossible to recover.The soldiers in Dunkirk are trying to return home to their families but their journey is forever scarred by the trauma of war.

In The Odyssey, the homecoming becomes the ultimate expression of this recurring theme.Odysseus wants to return to Ithaca but there's also a part of him that doesn't want to go home because going home means confronting what he has done.The physical journey is therefore also an internal one.

Nolan's protagonists often believe that if they can simply accomplish the external goal, they will be able to return to the life they want.But the problem is that the consequences of their actions travel with them.

Cobb cannot escape his guilt simply by getting back to his children.Oppenheimer cannot return to the world that existed before the atomic bomb.Bruce Wayne cannot save Gotham and then simply return to being an ordinary man.And Odysseus cannot win the Trojan War and then simply go home.

In The Odyssey, the first encounter between Odysseus and Penelope upon his return to Ithaca takes on the air of a religious rite of confession.Odysseus, disguised as a beggar, tells the story of what happened during the Trojan War from behind a partition punctuated by a small lattice, evoking the screen that separates priest and penitent in a Catholic confessional.

Athena joins him for one final time.Ultimately, Odysseus wants to be absolved of his sins.So does Oppenheimer, so does Cobb; so does Bruce Wayne.

Nolan has spent nearly three decades making different versions of the same film.He keeps returning to men who pursue greatness, lose themselves in the process and then have to confront the consequences of what they have done.

They are men trying to return home to their families, their identities or their former lives, only to discover that the journey has changed them beyond recognition.

The ancient Greeks believed that the stranger deserved hospitality.But societies throughout time have often turned the stranger into a scapegoat.

In Nolan's The Odyssey, the people from the sea are not simply the foreigners threatening civilisation.They are also the heroes who claim to be defending it.The threat, ultimately, comes home.

Civilisations often look outward for the source of their decay.They blame the stranger, the foreigner, the outsider.But sometimes the people who have done the most damage to a society are the ones who insist they are saving it.

Odysseus returns from the Trojan War as a hero.

But he also returns as one of the people from the sea.And like so many of Nolan's protagonists, he discovers that the greatest obstacle standing between himself and home was always inside him.