River Run (After the Dust Settled Series)

All Freya can remember is her sister, the basement, and the Man Upstairs. She has no memory of the world outside or of being warm or of not feeling hungry. And now her sister is gone. An unlikely ally shows her how to break out of the basement, but on the frozen banks of the Mississippi, Freya quickly discovers things worse than the Man Upstairs.

Freya is lucky to find Finn. He has a canoe, some supplies, and a vague idea about a place down south called Norlins. If they can dodge the slavers and avoid starving to death, the two of them might just have a shot at survival.