Dark Summer by Ali Sparkes
When Eddie discovers a secret passage in Wookey Hole caves, he just has to find out where it goes. But his amazement quickly turns to horror when he gets lost in the dark. He's underground, on his own, and nobody knows where he is . . . Until a hand reaches out of the blackness. A strange, pale girl helps Eddie get back to the surface, but she can't seem to leave the caves herself. Who is she? Or rather . . . what is she? And what other secrets is she hiding? Only one thing is certain - this is a summer Eddie will never forget. A captivating adventure from the author of Frozen in Time - winner of the Blue Peter Book of the Year Award!