Without speaking, everyone took a step back. "So, what do you think it..." but I never had a chance to finish my sentence. The room exploded in a cloud of noise and choking dust. A hollow metallic yell sliced through my head like the ringing of an enormous, tuneless bell. Then a pain at the back of my head broke through and I realised I was lying flat on my back, surrounded by groaning, coughing bodies. "Put your mask on " someone was shouting."I...