Found: 4 (House of Night Other Worlds)

Fog rolls into Tulsa, and with it comes Darkness.

Zoey knows the Darkness means something is up, and it looks like something involves Neferet. But Neferet can't possibly have been freed, right?
Meanwhile, Other Neferet arrives in Woodward Park to set this world's Neferet free from her grotto prison. Other Kevin and Other Stark are hot on their trail, but how can the new friends travel to this world without invoking Old Magick, and paying a costly - perhaps deadly - price?
Faced with a deadly enemy, Zoey and the Nerd Herd will have to band together with the unlikeliest of allies. But will they be powerful enough to defeat her old nemesis? Or will both worlds be destroyed and claimed by Darkness?
The thrilling conclusion to the House of Night Otherworld series from New York Times bestselling authors P.C. and Kristin Cast.