There's a memorable scene in the WWII movie Schindler's List where grateful Jewish workers thank their Nazi boss Oskar Schindler with the words: "Whoever saves one life saves the world entire."
But what if in saving one life you inadvertently plunged the world into the most catastrophic horror of all time? What if you saved the life of Adolf Hitler just as he was taking his first baby steps to becoming the most evil monster in history?
Carlow man Michael Keogh wrestled with that "what if" for decades up to his death in 1964. Because Keogh, from the village of Tullow, saved Hitler from being ripped apart by an ugly mob.
The remarkable life of Michael Keogh is the subject of an RTE documentary to be screened on April 2.
Keogh was a maverick adventurer from a long line of maverick adventurers.
His ancestors fought in the 1798 Rebellion. His great uncle Myles fought and died as second-in-command to Custer at Little Big Horn. His Fenian uncle Jack tried without much success to blow up Westminster Bridge.
So it surprised no-one when the 16-year-old headed for the US in 1907 in search of glory and mischief.
He joined the IRB group Clan Na Gael in New York but soon found himself in Texas fighting with US troops against Mexican banditos. Shot in the midriff, he returned to Ireland.
In 1913 he joined the Royal Irish Regiment of the British Army. A lowly private, he lectured his officers and spent a month behind bars after a court martial for voicing his strong republican views.
Despite these views, a fight was a fight, so he fought in the trenches until he landed in a German POW camp. Keogh had befriended Roger Casement in the US years earlier, and Casement now sought him out to head an Irish Brigade of prisoners willing to switch sides.
Privately the Germans treated Casement's Brigade as an Irish joke, but they were happy to play him along for the nuisance value he could deliver back in Ireland. But Casement's career as a gun runner was short-lived and after his execution in 1916 the Irish Brigade was effectively shelved by the Germans.
Keogh joined the German Army proper, where he rose to the rank of Field Lieutenant. In his regiment he met a fiery Lance Corporal called Adolf Hitler.
After the war, Germany descended into chaos as rival factions vied to fill the void left by the collapse of the old order. Keogh joined the proto-fascist Freikorps, who were sworn to smash Communism.
When Marxists attempted to set up a Bavarian Soviet Republic in Munich, the Friekorps wiped them out with shocking brutality. Peace had no sooner been restored than it was shattered by the noisiest man in Germany.
Keogh was duty officer at a Munich barracks when he was called to quell a riot that had erupted in a gym. What he saw was not exactly a fair fight.
A crowd of some 200 soldiers was kicking the living daylights out of just two. Some of the attackers were brandishing bayonets. The two victims were about to die.
Keogh ordered his men to fire a salvo over the heads of the mob. It did the trick. He dragged the two victims out of the gym "cut, bleeding and in need of the doctor".
It was a measure of Hitler's madness that he had entered the hall to provoke a reaction from 200 troops, by hectoring them with views that were already openly hateful.
As Keogh dragged him off to the guardroom for his own safety, the future fuhrer continued to spew angry comments.
Once there, Keogh recalled: "The fellow with the moustache gave his name as Adolf Hitler. It was the Lance Corporal of Ligny. I would not have recognised him. He was thin and emaciated from his wounds."
Keogh arrived back in Ireland in late 1919 as the War of Independence was coming to a boil. He linked with Michael Collins, trafficking guns from Germany.
After a decade here he moved back to Germany to work as an engineer. He attended one of the infamous Nuremberg Rallies, but after The Night Of The Long Knives in 1934 where Hitler killed former allies, Keogh began to fear for the safety of his German wife and children.
He moved back to Ireland on foot of a letter from De Valera promising him a job, but the promise went unkept.
After the war he'd say: "If we'd been a few minutes later or Hitler had got a few more kicks to his old wounds or he'd been shot -- what would have happened if we hadn't intervened and he'd died?"
It was a question with no answer.