A black and endless sky

"When estranged siblings Jonah and Nell Talbot head out on a cross-country road trip back to their hometown of Albuquerque in the wake of Jonah's divorce, the last thing they expect to discover in the Nevada desert is an abandoned industrial site built around a hole in the earth that seems to go on and on forever. Exploring it, they soon discover an underground cavern filled with corpses both fresh and ancient, indecipherable writing covering the stone walls, and a ghastly altar square in the middle of it all. After a seemingly-random accident befalls Nell underground, the two siblings emerge from the depths intent on finding help as Nell starts to exhibit strange, otherworldly symptoms - speaking in voices that aren't hers, knowing details about her brother's checkered past that she couldn't possibly have known before. As her condition worsens, Jonah comes to understand that the more his sister changes, the more danger they find themselves in, and when the siblings run afoul of a local criminal organization, the race is on to find help for Nell and escape before a violent, bloody end finds them. But of course, there are far worse things lurking in the desert... some of them living just underneath the skin. Pursued by the murderous gang and a mysterious stranger who knows far more about Nell's condition than she lets on, Jonah's journey home with his sister will cut across desolate backland highways, through casinos and derelict rest stops, ghost towns and abandoned churches. In their desperation, the two of them may find a way out, but they are no longer alone, and survival may cost them everything"--