Nori and Cooper's dark adventure continues in , the explosive sequel to series book one. Against all odds, Nori made it back to the safety of the 25th Parallel. But her heart is still somewhere below the Surface. She longs for the dark freedom of racing through the gritty Subterranean on the back of Sam Cooper's motorcycle. When Cooper shows up with a shocking secret he's kept for months, Nori is thrust back into the dangerous underground world. This time, a search for answers about her mysterious aversion to the sun reveals the ultimate threat to everyone left alive.