Jula slipped into the old library moments after lessons. It smelled of dust, chalk and old books, and the semi-darkness tempted her to hide from the world. The girl looked for a new reading corner every week, but today something was different - the bookcase with books about travel stood crookedly, as if someone had moved it. Hanging around the bookcase was Olek, her classmate, who always pretended to meet her by chance where she wanted to be alone. "Hey, Jula. Look!" - called out Olek, pointing to the floor. Just below the bookcase lay a metal plate that no one had mentioned before. The shape resembled a cellar trapdoor, but it was decorated with strange marks: circles, dashes and serpentine lines, like an ancient code. Jula knelt down and ran her hand over the engraved grooves. Then she felt a gentle vibration under her fingers, as if the flap had a pulse of its own. Olek struggled to stop himself from immediately opening the passage - he had always dreamed of finding something unusual. He gently lifted the flap. Light burst from within; not yellow, not white, but rippling blue-green rays. Jula looked at Olek, and Olek looked at Jula. For a moment they wondered what to do, but curiosity won out. After a brief hesitation, they slipped through the opening. Gravity seemed to have ceased to exist. They fell lightly, as if sinking on cotton cushions. Finally they landed hard on the soft, warm sand? They looked around. Instead of racks, they saw a vast desert under a purple sky. On the horizon they could see silver towers and huge, unseen trees whose leaves glowed with their own light. A sound came from the distance - a quiet, ringing sound, as if someone was playing on glass glasses. Jula felt her heart beating faster. Olek squeezed her hand. "We have to check it!" - Jula whispered. At that moment they heard a rasp behind them - their passage was slowly closing. Would they make it back in time? Or was their greatest adventure just beginning?