Roderick Gordon & Brian Williams 
Freefall [EPUB ebook] 

After DEEPER, can the TUNNELS adventure be any more dangerous? And where will it end? Will Burrows and his gang are far from finished as they free-fall down a subterranean pore. As they experience reduced gravity, the dark mysteries of the deep unfold and they discover a strange fungal shelf, which not only reveals artifacts from ancient civilisations, but clues to a lost land at the end of the Earth. The third in the thrilling Tunnels series — an international publishing sensation.