Lena sat in the library of her high school, trying to concentrate on her history reading, but her gaze kept escaping to the window. The spring sun was beating down on the rows of old books, bringing out the forgotten colours of the covers on the shelves. The library was already empty – only she and Igor, her friend from maths class, had stayed after hours as they prepared for the school Olympiad. When Lena got up to put her book down, one of the bookcases murmured quietly, as if moved by a gust of invisible wind. She looked at Igor and he shrugged his shoulders. ‘Probably some rats,’ he muttered, but Lena felt a shiver run down her spine. Suddenly, they heard a quiet clatter. Behind the last row, which she never particularly liked – because it hid a rusty radiator and cobwebs – there was a glow, as if a purple shadow had spilled out from behind a bookcase. Intrigued, Lena tugged Igor by the sleeve. ‘Come on, let’s see.’ Igor was always drawn to anything dangerous, so she didn’t have to ask for long. They squeezed through a dark crevice, hooked their backpacks over the protruding encyclopaedia volumes and stopped when they saw it – a mysterious portal. It looked like a sheet of water, reflecting light in shades of grey and purple, suspended in the air just above the floor. Lena knelt down, trying to touch the surface. Her fingers disappeared into the cool mist, as if she had put them in icy water. Igor pulled out his phone to record the whole scene, but the screen went blank as soon as he pointed the device at the portal. ‘He… he’s absorbing the light,’ he whispered, excited and terrified at the same time. Behind the portal were shapes – a strange staircase, glistening in the unfamiliar light, and the shadow of something that moved very slowly. Lena felt her heart beating faster. ‘Maybe it’s just some kind of art installation?’ She tried to laugh, but her voice sounded uncertain. Igor looked at her with a glint in his eye. ‘Or an entrance to another world. Imagine what we could see!’ Then a quiet, indistinct cry came from inside the portal. Someone – or something – was trying to contact them. Igor took a step forward; Lena grabbed his hand. The portal seemed to pulsate, and the air around them vibrated as if before a storm. At that moment, Lena had to decide: should she follow Igor and discover what was hidden on the other side, or retreat and close this mystery forever? For a moment they fell silent in suspense, staring at the shining portal that was slowly beginning to grow larger…