Nightfall is a sixth fiction novel in Keeper of the Lost Cities Series by Shannon Messenger, published in 2017.
All paths lead to Nightfall an ominous door to an even more ominous place and Sophie and her friends strike a dangerous bargain to get there. But nothing can prepare them for what they discover. The problems they’re facing stretch deep into their history. And with time running out, and mistakes catching up with them, Sophie and her allies must join forces in ways they never have before.
In this spectacular sixth book in the New York Times and USA TODAY bestselling Keeper of the Lost Cities series, Sophie must uncover the truth about the Lost Cities’ insidious past, before it repeats itself and changes reality.