I had two grandmothers with floral names: Rosa and Margarita. They were too old to enjoy their retirement, and they were alone. What I didn’t have were grandfathers. One had died on my second birthday and I don’t remember him. The other, Vasily, suddenly appeared when I was about 10, out of nowhere, with the words: “I am back.”

Until that point, I hadn’t known about his existence, so I was astonished, amused and happy to get a grandfather.

I spent my childhood in the ancient city of Kiev, the biggest city in the Soviet Union after Moscow and Leningrad. We lived in a 14-storey apartment block on the left bank of the majestic Dnieper river. Our entire neighbourhood district was built after the second world war and seemed to have no past, only a shiny Soviet future. We always said “the war”, as if it were the only one, and everything around us was about this war. No family was spared. The perished were our common heritage, almost the only property we had, and each family story seemed to reflect a tiny part of a big history.

My family was small. I had almost no relatives because of the war. Whole family branches had perished. But there were many who had fewer relatives than I did. I had no reason to suffer. However, I always dreamed of a big family at a long table.

A few months before Vasily returned home to his wife and younger daughter after a 40-year absence, I remember hearing a confused old woman ask loudly on a tram, “Has the war already ended?” as if she was talking about the next stop. She was not that wrong. My grandfather “came back” from the second world war in 1981.

The explanation I was given at the time was that he had disappeared at the beginning of the war, during the encirclement of Kiev in August 1941. He was captured by the Germans and spent years in their camps as a Soviet prisoner of war. The family knew that he had survived but, for some reason, he just didn’t come home. But now here he was, back finally.

It was a very vague story, satisfying perhaps for a child, but disturbing later. I never asked him directly where he spent these 40 years, or how he reached “home”. At the time, the family treated it as good news: the second world war was finally over, now, at the beginning of the 80s, because my grandfather had come back. It was a miracle of the sort I knew only from books.

A family photo of Rosa, Vasily and Lida, showing the tear where Vasily had been removed. Photograph: Courtesy Katja Petrowskaja

As a child, I was in love with Greek mythology, with the Trojan war and the return of Odysseus. The return of my grandfather fitted in with these tales, and I was proud that my once beautiful grandmother had waited all those years for him. Rosa had never remarried, or even let anybody get close to her – Penelope, Odysseus’s wife, waited only 20 years. I felt that my ancestors were gods and heroes, or almost.

My mother took Vasily in, and he spent the last year of his life at our place, sitting in an armchair and smiling. That armchair seemed to be the apex of his existence. He was confident and radiant in his silence, as if he had a dark secret and was happy that his grandchildren were spared it. I have spent years since then trying to understand his silence, and his return. Between the armies near Kiev in 1941 and the armchair in our apartment in the early 80s, a black hole slowly grew.

He was a beautiful old man and I felt very protective of him – he was my newly born grandfather, somehow younger than I was, and I had to look out for him.

Years later, as I began to search out his story, he catapulted me into the middle of the war. I followed him, along with masses of soldiers, from Kiev to Volodymyr-Volynskyi prisoner-of-war camp north of Lvov. Then I followed him to another PoW camp in one of the most beautiful Austrian landscapes near Salzburg, then to the site of the concentration camp at Mauthausen.

I was haunted by the idea that he had seen or done something during imprisonment that was so inhuman that it had made his return to his family impossible. I searched for a specific point in his journey, his “point of no return” – something that might explain his absence for so many years.

A photograph of Vasily taken in the 1970s. Photograph: Courtesy Katja Petrowskaja

I was searching for him in the archives, and even there he almost didn’t exist, as if he were a fiction. I found out that he was encircled, together with a million other Soviet soldiers, and became one of more than six million Soviet prisoners of war, who were excluded and erased from memory. They were considered traitors; they didn’t belong among the “victors” over fascism. Rather, they became double victims of the Soviet system: imprisoned by the Germans, because they were so poorly armed and led, and then, if they survived, imprisoned by the Soviets. Suddenly, I realised that his small story spoke of the fate of millions and, in looking for him, I was caring for all of them.

My grandfather was lucky to spend only two or three years in Soviet “filtration camps” following the war. I discovered afterwards that, in fact, he had come home from the camps, but only for a short time – he could not live with his family any more and so he left again. Why? Was it survivor’s guilt? The impossibility of a normal life?

The story might be simple: he had another family – he was helping the widow of a friend who had died and stayed with her and lived for a time after the war moving between two families, but my grandmother threw him out. He then spent many years alone in a small village in western Ukraine, returning to Kiev when he was old. He came back to Rosa at the end of his life and maybe it was too late. When I say that I remember them kissing, my mother gets angry with me.

We have only one family photo that survived the war: it is of my grandmother Rosa (pregnant with my mother), my grandfather Vasily and Lida, their elder daughter. It is torn in half, as if someone sought to remove Vasily, but then thought better of it. Perhaps it was done just after the war, when he returned briefly, only to leave again. Rosa and Lida stayed together and Vasily was cut off.

Then, four decades later, there he was, sitting and smiling, happy to be home, to be with us. His silence was something I was not used to, because all of us were talkative, energetic, always full of untold stories. It might sound like a joke, but Rosa and Lida and their ancestors had, for some generations, taught deaf children to talk. It was the family vocation. But Vasily was mute.

Vasily was the only Ukrainian in the family, all the others were of Jewish origin, a thousand miles away from tradition, but it did not matter in this war. Without this grandfather, we lacked connection to the soil.

Katja Petrowskaja with her parents and brother. Photograph: Courtesy Katja Petrowskaja

He was the only one who had his own garden plot on the edge of town, so I got a grandfather and a garden to boot, allowing me to experience a small fairytale at the end of my childhood. My parents, and everybody we knew, had huge libraries at home, their only property and joy. My grandfather had a piece of land, a dacha, which I visited only a few times.

All his neighbours planted potatoes and tomatoes, putting their property to some practical use, but Vasily turned his dacha into a paradise full of roses, encircled by white raspberry, which I had never seen before, and in the middle of the garden stood one paradise-apple tree.

I really don’t remember him talking, apart from a few words such as “yes” or “good”, but I do remember the names of roses, and these are the words he left me: Dolce Vita, October Stars, Chinese tea roses, Gloria Dei.

I don’t remember his last days, but I do recall him standing in the middle of his rose paradise, cultivating his garden.

• Maybe Esther by Katja Petrowskaja is published by Fourth Estate on 8 February, £14.99