Of the many bleak moments that have lodged in my mind since reading this extraordinary book the most unshakeable is the image of the once dignified Otto Neumann, walking to his death in torrential rain, with black shoe polish running down his face and into his eyes. Thus was his fate sealed as the silver hair revealed beneath ensured he was deemed too old to be selected for work. He was despatched instead to the gas chambers of Auschwitz.

But if this downpour, in a hideously crazy world, can be considered bad luck — after all, Otto and his wife Ella had by then managed against the odds to survive in the hell that was Terezin for two years — Hans, their young son then in hiding, was to have moments of astonishing good luck, which ensured his survival. After the war, perhaps his greatest luck was to have a daughter who has devoted years to unravelling and reconstructing the wartime experiences that he could never bring himself to talk about with anyone, least of all her. Yet he clearly wanted her to write this story, and on his death in 2001 left her a box of papers which, she believes, gave her permission to continue the search.

Actually the search began much earlier, when Ariana, brought up Catholic in Caracas, played a game with some school friends pretending to be part of a spy detective club which they called the Mysterious Boot Club. One of the first documents she discovered was an identity card from 1943 with the name Jan Sebesta and a Hitler stamp but a picture of her father as a young man. Yet when she ran screaming to her mother that her father must therefore be an imposter, nobody would tell her any more. Any discussion of what came before his successful life as a wealthy industrialist and art collector in Venezuela, where he moved with almost nothing in 1949, was not encouraged. And yet there were occasional and puzzling glimpses, such as when in 1990 he took his daughter back to Prague and, stopping at the wire mesh fence along the railway tracks of Bubny, broke down and sobbed uncontrollably. He could not bring himself to tell his only daughter about the devastating event that had taken place there in 1942. She had to find out for herself.

Over the years since her father’s death Neumann has located and pieced together hundreds of documents and clues to create this gripping account of her father’s wartime survival. At the core of the book is the account of how he first avoided deportation by hiding in a specially built narrow partition in his family’s Prague paint factory. When his existence there became too dangerous, he and his friend Zdenek, in a sense the true hero of this book, hatched a daring scheme for him to travel to Berlin with forged papers and work under an assumed name in a Berlin paint factory which was developing a new camouflage system for German rockets.

The story of how this Czech Jew, wanted by the Gestapo, hid in plain sight in Berlin, had a relationship with a German war widow, was praised for his innovative work by an openly Nazi boss and went about the German capital in 1943 is breathtaking. Towards the end of the war he even became a spy, passing on information to a Dutch fellow worker in the paint factory.

‘What Remains’ — part of this powerful book’s subtitle — is a modest phrase for what is a giant achievement. For what remains is so vast, so much more than one life brought out from the shadows: it is a daughter’s deep love and humanity towards a complex and occasionally difficult father who tried to shield her from the pain of knowing about his earlier life, but it is also the story of a whole family lovingly recreated. Especially revealing is the courageously tender way Neumann writes about the grandparents she never knew and has now shared with us, a middle-aged couple who approached the devastation of the camps with markedly different attitudes to life.

Ella, mildly flirtatious, would have done almost anything to survive (the almost is important), resulting in her husband Otto’s accusations that they had a ‘failed marriage’ and that his wife was having an affair with the man in the camp for whom she was acting as housekeeper. Neumann, far from being critical, simply shows how impossible life was, grateful that at last she has found the family that was veiled in silence. ‘I have retrieved an essence of them and I carry them in my heart; now that they are finally with me I refuse to say goodbye.’

One of the key strengths of Neumann’s memoir is her dogged research into astonishing details of daily life in the camps — thanks partly to letters her grandparents smuggled out but also from accounts written by those who knew them. The story of her grandfather, exhausted, condemned to death by the failed shoe-polish hair dye in the November rain, came from an eyewitness in the same transport. This book is chillingly sad, but overall optimistic, and by no means simply another Holocaust story. It’s a treasure to be savoured as testament of the human will to survive.