Spensa and her comrades have won the battle against the Krell, but the war is not over. If people remain locked in the Placer, sooner or later the enemies will achieve their goal and destroy the remnants of humanity. To find a way to salvation, Spensa, taking on the guise of an alien, goes into the very heart of enemy territory. And he discovers that not everyone there hates people. But a common threat looms over both the Krell and humanity - delvers, mysterious creatures coming from an unknown space and capable of destroying all life on the planet in a matter of seconds. The enemy of my enemy is my friend. Or is it not so?