At around midnight one evening in April 1949, a handsome middle-aged man alighted from a train at Rome's central station. With no place to stay and just a handful of contacts, he would have been feeling extremely insecure and anxious.
But then this 47-year-old was accustomed to such feelings, because he had been on the run for the past four years — ever since the end of the war. For over three of those years he had hidden in huts and shacks high in the Austrian Alps, accompanied by a former private in the SS. They survived on whatever provisions his ever-loyal wife could haul up to him.
With British and American troops scouring the valleys below, the man would have reflected on his previous life during the war, when he was Nazi governor of the Polish province of Galicia, a full general in the SS with the power of life and death over millions, according to the Daily Mail.
And it was a power that the aristocratic Baron Otto Gustav von Wächter had been more than happy to wield. During his two years running the province, an estimated 500,000 Jews were sent to their deaths, while hundreds, perhaps thousands more, were killed in reprisals.
As a major war criminal, indicted for war crimes by the Polish government-in-exile as early as October 1942, it was hardly surprising that as soon as the war ended, Wächter — the name is pronounced 'Vekkter' — hotfooted it into the hills.
But on that night in Rome, the former Nazi bigwig was now just small fry, a piece of flotsam on the flood of humanity surging around a ravaged Europe. He had no friends, no power, and no idea of what the future held.
The twisting tale of the career and flight of Otto von Wächter sounds like something that would make a superb film or a TV box set. However, surprisingly perhaps, it is in fact the subject of a ten-part podcast produced by the BBC called Intrigue: The Ratline.
For those not up to speed with the bewildering number of ways in which one can access media these days, a podcast is typically a series of audio programmes that can be downloaded and then listened to on a PC, smartphone, laptop, tablet or iPod.
Unlike a regular radio programme that has to be tuned into at a scheduled time, a podcast has the immense convenience of being available whenever you want it.
Podcasts are now big business, partly due to the rise in those about crime, whether fictional, or — like The Ratline — historical.
The most popular such podcast has been a series called Serial, which started in 2014 and was about the murder in 1999 of an American schoolgirl called Hae Min Lee. It has been downloaded 208 million times — the type of listening figures that no radio station could ever hope to boast about.
There's no doubt the BBC is hoping The Ratline will attract a similar number of downloads, and although it has not released any figures, it certainly looks like the podcast is going to be a hit.
Not only do the critics love it, with the doyenne of radio critics Gillian Reynolds calling it 'an astounding piece of work, miles better than Serial', but even the quickest of scans through social media sites reveals that people are lapping it up.
But why is The Ratline proving so popular? The short answer is that the series has it all: Nazis, spies, the attics of German castles creaking with secrets, shady bishops, a love story, murders and other horrors — as well as an old man trying to make sense of his father's legacy.
That old man is Horst von Wächter, who ardently maintains that his father was a 'good Nazi', and was not responsible for the terrible crimes committed against the Jews and so many others when Otto was the governor of Galicia.
Trying to establish the truth is the podcast's presenter, Philippe Sands, a highly respected barrister who specialises in international law and has appeared as a counsel and advocate in front of — among others — the International Court of Justice and the International Criminal Court in The Hague.
However, Sands's interest in the von Wächter family and the fate of Otto is not just rooted in his professional calling, but also in the shocking fact that his grandfather and several other members of his family were murdered by the Nazis in Galicia during the war.
This means, of course, that Horst's father was responsible for their deaths, which makes the relationship between Sands and Horst a tricky one to say the least.
Despite the fact that the two men have such different interpretations of Otto von Wächter's culpability, throughout the series Horst is willing to share with Sands all manner of his family's private items.
It is in the dusty attic of his magnificent schloss where he reveals hundreds of letters written by his parents to each other during the war, as well as numerous mementos, including a book presented to Otto on his 43rd birthday by none other than the dreaded head of the SS, Heinrich Himmler.
The letters between Otto von Wächter and his wife Charlotte — which are read by Stephen Fry and Hollywood star Laura Linney — are extraordinary because their very mundanity sits in such naked contrast to the horrific nature of his day job. Take, for example, the letter von Wächter sent on August 29, 1942.
'Things are going very slowly in the garden unfortunately,' he wrote. 'There's not much labour around. The Jews are being deported in increasing numbers, and it's hard to get hold of powder for the tennis court.'
In just three brutally simple sentences, von Wächter encapsulated the essence of that phrase, made famous by philosopher Hannah Arendt after the Holocaust, 'the banality of evil'. He worries about his garden as many people do, but then immediately switches to the 'deportation' of the Jews — a process that we today know all too well actually meant mass murder.
And then, most chillingly of all, the most notable thing he has to say about this destruction of human life is about how having fewer Jewish labourers will affect the upkeep of his tennis court.
Sands slowly builds up a picture of von Wächter, charting his life from a privileged young man to one of the first Austrians to embrace Nazism in the early Twenties.
It was his love of fascism that would see von Wächter twice become a fugitive. The first time was in 1934 in the wake of his participation in the killing of Austrian Chancellor Engelbert Dollfuss in a failed Nazi coup attempt. The second time was in May 1945.
His political life is contrasted with his romantic endeavours. We see von Wächter fall in love with his future wife, Charlotte. We hear how she regarded him as 'dashing and radiant and kind-hearted', and how she 'loved him and would have gone through fire for him'.
It is to Sands's immense credit — as a man whose own family perished partly through the orders issued by von Wächter — that he presents his subject both as the committer of genocide as well as a loving family man with a wife and children. It is only when we see such murderers in the round that we can fully appreciate how even 'normal' people can commit abnormally vile acts.
After the war, Sands tracks von Wächter's progress from Galicia to the Austrian Alps, and eventually to Rome, where he ends up consorting with the most diabolically shifty characters imaginable. Among them is the notorious Bishop Alois Hudal, the head of the Austrian-German congregation in Rome, who assisted many Nazis in their escapes.
It would certainly spoil the plot to reveal much more, and the number of surprises that Sands dishes up will doubtless make many listeners need to pause their iPods while they take it all in.
As the author of a history about the largely ineffective hunt for Nazi war criminals, there is much about the podcast that to me rings absolutely true.
But Sands does fall victim to the notion that there was a Nazi escape organisation called 'the Ratline' — indeed the podcast is named after it. In reality, however, there was no such thing, and neither was there a post-war Nazi plan for escape called the 'Odessa', or anything like it. In truth, the Nazis escaped by using various ad hoc networks that were maintained through informal word-of-mouth rather than through an official organisation.
The idea, then, of a single entity such as the 'Odessa' or the 'Ratline' is the stuff of fiction.
When I interviewed the war criminal and former Gestapo officer Erich Priebke, who had successfully escaped to Argentina after the war, about whether such an organisation existed, he simply laughed and told me that he wished there had been, as he arrived in South America without a bean.
But none of this should detract from the thrilling tempo and the jaw-dropping revelations in Sands's podcast, which sheds light on a largely forgotten and extremely dark period of history, complete with characters more evil than even the most lurid of box sets.
Guy Walters is the author of Hunting Evil. Intrigue: The Ratline can be found at bbc.co.uk/podcasts or by searching the podcast app on your smartphone or tablet.
Police found in a notebook the names of 11 'people-search' websites.