The Mysterious Arrival introduces Alex, a spirited 13-year-old with a penchant for mischief, as he moves into an eerie old house on the outskirts of Brighthaven. Driven by curiosity and armed with a mysterious map, Alex embarks on a quest to uncover a hidden labyrinth beneath the city rumoured to hold ancient treasures. Venturing into a quiet park, he encounters an enigmatic talking fox that warns him of the labyrinth's dangers. Undeterred, Alex discovers the labyrinth's entrance, only to meet Lila, a resourceful girl with her own knowledge of its perils. Together, they face shifting paths, cryptic trials, and an awakened labyrinth testing their courage and unity.