For most of the last forty-eight hours Donna Yorke had hidden under a desk in a corner of the office where she'd worked since the summer. Without warning her familiar surroundings had become alien, nightmarish and cold. On Tuesday morning she had watched the world around her die. Along with the rest of her work colleagues Donna worked an early shift one week in four. This week it had been her turn to get in first and open the post, switch on the computers and perform various other simple tasks so that the rest of her team could start working as soon as they arrived at their desks. She was glad that everything had happened so early in the day. She'd watched four of her friends die. If it had happened just half an hour later she'd have seen the other sixty-or-so people in the office suffer the same sudden, suffocating death. None of it made any sense. Cold and alone, she was too terrified to even start trying to look for answers. From her ninth floor vantage point she had watched the destruction wash across the world outside like a tidal wave. Being so high above the city she hadn't heard anything. The first sign that something was wrong had been a bright explosion in the near distance, perhaps a quarter of a mile away. She'd watched with morbid fascination as a plume of billowing fire and dense black smoke had spewed up into the grey air from