At the centre of the earth, in a world that no-one knows exists, Will is in trouble. His enemy, the Styx, are right behind. They'll follow him to the end of the world—any world. Meanwhile Drake—with help from the unlikeliest of allies—is preparing to fight the Styx from above. But will his daredevil plan bring him closer to victory...or to certain death?

The fourth fantastic adventure in the Tunnels series from acclaimed authors Roderick Gordon and Brian Williams.