Darkness covered the city as Lena, Michal and Ada turned into a narrow alley leading to an old library that had been closed for years. The place had always inspired a mixture of fear and fascination in them. It was said that among the cracked bookcases and dusty volumes lurked more than just the memories of past readers. Their breaths could be heard louder as they approached the fence. Michael, traditionally the bravest of the three, leapt through a hole in the netting and shone his torch at the rusty front door. To his surprise, it was slightly ajar, as if someone had recently opened it. - 'Do you think someone got in here before us? - whispered Ada, keeping close to Lena. - 'Or someone invited us here,' replied Michal with a smile, but his voice betrayed uncertainty. Inside, the air was heavy, smelling of old age and dampness. As they entered the main room with its stained-glass window, they noticed that a candle was burning on one of the tables. The glow gently illuminated an old parchment and something that looked like a metal key. Lena held her breath. The parchment was inscribed with strange symbols, similar to those they had once seen in books about alchemists. Ada shuddered, touching her friend's arm, and Michal was already reaching for the key. Suddenly, there was a slight rustling in the depths of the library - as if someone was knocking over books or moving something heavy across the floor. The three of them froze. Someone, or something, definitely did not want to be found. Suddenly, the candlelight trembled, the door to the reading room creaked open and a shadow flitted across the wall. Lena, Michal and Ada looked at each other, uncertain whether they should retreat immediately or follow the mysterious shadow, which was clearly trying to lead them somewhere....