figure out is why they would want to hide from us and then attack us. They don't even know us. You were there on Mars. Did something happen that you didn't tell me? What was one of their ships doing on Mars anyway? It suggests they've had some connection with humans in the past?"
As she talked, a strange change came over Morden's face. The muscles went slack, his carefully composed expression melting away. He reached into the pocket of his jumpsuit, and as she realized he was going to pull out the PPG, she remembered his encounter with this race on Mars, his shiny tools, his smooth palms, Chang's warning to her, and Donne's, and his statement, almost a warning in itself: "I find I'm much more effective if I go about my job quietly."
As the PPG came clear of the pocket and began to rise, she shoved him, hard. The gun went off with a reverberating blast. She lost her balance, heard rocks falling, and then a flash and she hit the cave floor. She covered her head with her arms and tucked her body into a ball. She'd been in rockfalls several times before, all minor, so she'd always thought Chang had been joking when he'd described the cave-in at Al-mover: "it was like being an ant in the center of the bowling pins when God hits a strike."
But that was exactly what it felt like. The world collapsed around her, huge rocks clashing and crashing in a great cascade like thunder. One rock slammed into her legs, another into her back, the heavy gravity increasing the impact. The ground shook as if she were in the middle of an earthquake. Her arms squeezed desperately around her head. From the thunder, the rockfall seemed to be concentrated a few yards up the passage, where Morden's PPG must have hit. Two great slabs of rock shattered against the cave floor, and then the rumbling