"But when I close my eyes, I first fall as if drowning into the silty waters of the Chari River, which traces the border between Chad and Cameroon, and into which so many men, women and even children were thrown, sometimes still alive, their hands knotted behind their backs, or tied up in a shoulder bag. I sink with them towards the sand and the clay, down amidst the green and the brown, passing purple weeds, shards of pottery, and crocodile scales...