When Harry Michielsen is quietly enjoying a beer on the Marktplatz in Halle an der Saale, he sees a murderer walk past.

It was more than twenty years ago, the files have been closed, the detectives have retired, the case forgotten. What should he do? Is there any point in dredging everything up again?

After a sleepless night, he lies in bed in the early morning light, deliberating. Beside him sleeps his wife, who knows nothing about any of this. He relives that terrible year 1989, the year of Tiananmen, the year of the Wall, the year of the murder. On a summer night, made for loving and gazing at the stars, the family of his old friend Luc Van Eynde fell victim to the bullets of a gang of bandits. The crime was never fully solved.

It was also the year in which Harry was made a particularly attractive offer: an unknown seller offered him an original letter by the great mathematician Georg Cantor, a letter that would shed more light on the life of this tormented genius. A once-in-a-lifetime opportunity, a chance to break through as a writer, even though Harry initially had no idea where he would get the money he needed.

Harry is not the only one lying awake: Mia, his wife, has her own worries. In that same year of 1989 she lost track of her best friend Else. Her bosom friend from Halle had become involved in the popular resistance against the East German regime and lost her job. Mia's well-meant help backfired badly: after the fall of the Wall, Else disappeared without a trace.

And now, in the sunny spring of 2011, fate ensured that they could travel to Halle, each with their own purpose, each with their own dream.

The appearance of the murderer threatens to throw everything off course. Harry wants to get to the truth at any cost; Mia is swept along in the deadly undercurrent.

De Standaard der Letteren: rating ***