And so it goes on. To the third and fourth generations. The urge to know what happened, to investigate secret histories, to reveal hidden truths, to discover and uncover every last scrap of Shoah history before it all fades indemonstrably into the past.

The Ratline is barrister and author Philippe Sands’s meticulously documented sequel to East West Street, his award-winning, multi-dimensional exploration of how his forebears became victims of Hans Frank, Governor General of occupied Poland. His follow-up, a synthesis of bravura storytelling and investigative journalism, focuses on another of the perpetrators of those crimes: Frank’s deputy, the Governor of Galicia, Otto Wächter, under whose watch Sands’s Lvov-born grandfather was murdered.

Unlike Frank, who was hanged at Nuremberg, Wächter was indicted for mass murder but fled justice at the end of the war. And yet, in spite of the existence of the so-called “Ratline”, a clandestine organisation that helped thousands of Nazis escape to South America, Wächter died in a church-run-hospital bed in Rome in 1949 — which is where Sands’s account begins.

In the spirit of his eyebrow-raising epigraph from the Spanish novelist and documentarian Javier Cercas — “It is more important to understand the butcher than the victim” — Sands excavates, with forensic precision and the narrative flair of a Le Carré, the life, loves and crimes of the man responsible for the deaths of more than 100,000 people.

But although his text may read like a thriller — with revelations about Wächter’s years on the run (including the help he received from the Vatican and the possible collusion of the Americans) interwoven with the record of a decade’s-worth of Sands’s assiduous international sleuthing — this is still a book in rigorous pursuit of historical truth.

A key actor in Sands’s heroic quest is Horst Wächter, one of the two children of his sought-out Nazis (the other was Niklas, son of Hans Frank) whom Sands had met while researching his earlier book. Without Horst, it is doubtful that this current book would have been possible, for Horst was in possession of thousands of letters, postcards, diaries and interviews bequeathed to him by his mother, Charlotte, Otto’s wife, who stayed in contact with her husband after the war.

In due course, Horst — whose reluctance to fully face up to the crimes of his father is one of the intriguing psychological sub-plots within The Ratline — allowed Sands and his team of researchers access to this historical gold-mine.

The mystery of Wächter’s premature death, whether from poison probably administered by an unknown revenging hand, or self-inflicted after swimming unwittingly in the toxic water of a nearby river, now remains beyond anyone’s certain knowledge.

Which is perhaps as it should be; for, although Sands has done all that is humanly possible to find an answer, he has written a book that reminds us, again, that in some essential way the past is unknowable, however much, and for however long, later generations still seek to know it.

Howard Cooper is a rabbi and therapist