The Dead-Tossed Waves (Forest of Hands and Teeth Trilogy)

Gabry lives a quiet life, secure in her town next to the sea and behind the Barrier. She's content to let her friends dream of the Dark City up the coast--home is all she's ever known and all she needs for happiness.
But life after the Return is never safe.
Gabry's mother thought she left her secrets behind in the Forest of Hands and Teeth, but like the dead in their world, secrets don't stay buried. And now, Gabry's world is crumbling.
In one reckless moment, half of Gabry's generation is dead, the other half imprisoned.
Now Gabry knows only one thing: if she has any hope of a future, she must face the forest of her mother's past.