The second nigun was more intricate than the first. Dovidl found himself harmonising under his breath, assimilating its cadences. Music, these rabbis must have known, clings to the brain like a barnacle. In the aged and confused, it is the faculty that fades last, the final memory. For the faceless victims, it was a lasting memorial that could never be denied or vandalised. The swirl of names continued in song. When the Young Rebbe reached ‘. . . Rapoport Shimon-Zelig und Esther mit Kinder Pessia, Malkeh, Basya-Beyla’, Dovidl started in recognition. The Rebbe gave a fermata gesture, ending the chorus with ‘Rapoport, ay Rapoport, ay Rapoport, yehi zikhrom boruch.’

‘Zygmunt was Shimon-Zelig in Hebrew?’ he asked.

Dovidl nodded, tears spilling from his eyes.

‘Blessed be the Judge of truth,’ said the Rebbe. ‘My father knew him. He was in our transport to Treblinka, August 1942,’ he confided, still swaying. ‘When we arrived, they put women and children to the left and sent them to the gas. The date of your mother’s death and your sisters’, the date for you to say kaddish, ay Rapoport, is the seventeenth of the month of Av, remember that, seventeenth of Av, ay Rapoport.

‘Some men were spared for maintenance tasks. Your father, Shimon-Zelig or Zygmunt, was in the same barracks as the Alte Rebbe, on the same work-detail, the same forced march when the camp was closed. He gave up his holy soul, on the twelfth of the month of Shevat, the month of Shevat, on the twelfth you must say kaddish, ay Rapoport.

‘And one more Rapoport, a cousin Chaye-Rivke, came out alive from the place of destruction. Ay what happened to her, Rapoport. She was set free by the Russians and set out to walk south, to the south, until she came to a port and hid in a ship that took her to the Land of our Fathers. And there she met a man called Shteinberg, who changed his exile name to Har-Even in Hebrew and worked on a farm near the Holy Town of Safed, ay Rapoport. And she married, ay Rapoport, and she has a child, God be thanked, ay Rapoport. May God wipe a tear from all faces and remove His people’s disgrace from the earth, for that is the word spoken by the mouth of God.’

The Young Rebbe fell silent, opened his eyes. His face, like the prayer-room, looked as if it had never seen daylight. ‘Ich bin der Welt abhanden gekommen,’ came to Dovidl’s mind – the title of a lonely Lied by an Austrian Jew, Gustav Mahler: ‘I am removed from the world’. This unworldly rabbi, barely older than himself, had experienced all the world’s evil and emerged, somehow, secure in his unworldliness, brandishing his father’s song like a shield against oblivion. He was, in the prophet’s words, ‘a brand plucked from the burning’.