The mystery of the old school map

When the bell rang to announce the end of classes, four friends - Laura, Tom, Lucas and Anna - met in the school's history club, as they did every Tuesday. On this day, however, instead of spending time discussing recent historical events, they decided to find the mysterious old school cellar, which they had learned about from archive documents. According to these documents, the cellar was used in the 1950s and 1960s to store old school items. However, before they could discover how to access it, they accidentally broke into it during a football match, when a badly kicked ball hit an old wall and revealed a hidden entrance. Descending the soggy steps, they reached a small room filled with old furniture, boxes and dusty equipment. Among them they found an old map that looked at least fifty years old. All the rooms of the school were marked on the map, including some that no one knew about. What intrigued them most was a strange symbol marked in one of the corridors on the third floor - a place that seemed perfectly normal. Excited by this discovery, they decided to investigate the place. However, just as they were starting to solve the mysterious code on the map, the old school cleaner, Mrs Mabel, descended into the basement. Surprised by their presence, she said only one word: 'Run away!