The rain drummed against the roof of the old library as Lena searched the shelves for a book for her algebra paper. No one expected her here after lessons - not even herself. In fact, she just wanted to spend a moment in silence. Instead, her gaze was drawn to a thin, untitled volume wedged between 'Practical Alchemy' and 'Chaos Theory'. Intrigued, Lena reached for the book. The pages were covered in even, fine handwriting, and someone had slipped a folded letter at the end. Her heart began to beat faster as she unfolded the paper. "Come to the roof of the school at midnight tonight - let the smell of incense guide you through the fog. Bring something you are afraid to lose." For the rest of the day she couldn't stop thinking about it. Who could have left such a strange message? Was someone making fun of her? Or was it some secret school initiation that she had only heard about in rumours? At midnight Lena slipped out of the house. The fog was thick, the light from the lantern barely breaking through the white veil. In her pocket she clutched a silver pendant, an heirloom from her grandmother. She was afraid of losing it, but she didn't have a better thing - it only seemed suitably important. Several young people had already gathered on the roof of the school. Most of them she did not know, although their faces seemed strangely familiar, as if she had seen them in dreams. One of the girls, dressed in a long coat, handed her a small vial of blue liquid. "Drink it to see what is hidden from ordinary eyes." She hesitated, looking at the mysterious silhouettes illuminated by candlelight, incense smoke dancing between them like transparent snakes. Lena felt that this was the limit - the moment after which nothing would be the same. The air sparkled with tension as she raised the vial to her lips....