On her twelfth birthday Cecilia goes out with her parents and sister to celebrate with a visit to a museum. On their way Cecilia drops the marble that her sister gave her as a present, and running to pick it up she is taken away on an empty underground train into a dark and deep tunnel. The fun family outing becomes a much more serious mission when Cecilia finds that she and her marble have a very important role to play in freeing the inhabitants of the tunnels from the tyrannical rule of the Corvus.A truly inventive, clever and magical story about the power of friendship and the importance of self-belief by debut novelist Nadine Wild-Palmer.