At the foot of a pine tree, Grzegorz Kwiatkowski bent to touch the black, moist shapes nestling amid the fungi and leaf mulch. “I’ve been monitoring this area now since 2015, and always hope I won’t stumble upon anything any more and that one day the entire area will have been cleared,” he said. This, however, was not that day. The 39-year-old poet, scholar and rock musician was walking in the forest just metres from the perimeter fence of what was once the Stutthof Nazi concentration camp in the German-annexed territory of Poland, and is now a memorial site in...