It was one of those silly questions you sometimes ask when you want to reassure someone you're a little concerned about. But a silly question can sometimes be answered in a totally unexpected way--suddenly, terribly and with explosive violence. It can be answered by a voice of thunder out of the sky, or a wild, savage cry in the night, or in a quieter way, but with just as terrifying an outcome. There are a hundred cataclysms of nature which can give the lie to what you thought was only a silliness. No matter where you are or how secure you feel, never ask what could happen in a world where nothing is sure, where no one is ever completely safe. Death is death. From end to end of his big estate may be a lifetime's journey for some men. But he can cover the distance with the speed of light, because Death is one space traveler--the only one--who knows exactly how to outdistance light. Even if you're alone in a steel-walled vault it's a dangerous question to ask. It's ten times as dangerous when you're descending a swaying metal corkscrew forty million miles from Earth and there may be someone eighty feet above you who has failed twice as Death's emissary and would be covered with shame if it happened again. I felt hardly anything for an instant when the dart sliced deep into the soft flesh between my shoulder blades. I didn't even know it was a dart and kept right on walking. It was as if a bee had stung me--a tired bee who couldn't sting very hard. There was just a little stab of pain, a burning sensation that lasted less than a second. I felt it, all right. But it didn't startle me enough to stop me dead in my tracks. A thing like that seldom does, if you're moving steadily forward. It takes a second or two after you've felt the pain for the implications to dawn on you. When they did the pain was back, and this time it was excruciating. My whole shoulder was laced with fire, as if a red-hot iron had been laid against it. If right at that moment I'd smelled an odor of burning flesh I'd have been sure there could be no other explanation, despite its transparent absurdity. Even then I kept right on walking. I staggered a little but I bit down hard on my underlip to avoid crying out. I didn't want to alarm Joan until I was sure. It could still have been just a very severe muscular spasm--the kind of agonizing cramp that can hit you in the leg sometimes in the middle of the night, so that you awake out of a deep sleep bathed in cold sweat, and with your teeth chattering.