Ethan and Shawna have never seen the sun, but that's not the only way they've been kept in the dark. Born in an underground mega-city built to preserve the human race in the aftermath of global nuclear war, these siblings have a few secrets of their own.

What Ethan saw shouldn't be possible, and now it's up to the twins and their friends to unravel generations of secrets and lies. If they succeed, life will change for everyone. If they fail, they will never see each other, or their family, again.