Zoey and Trey have been living underground their entire lives. They think that the world was destroyed 90 years ago they were lucky enough to survive. They thought nothing of escaping.
One day they overheard people talking about how there might be population on the surface. Zoeys interest was sparked and remembered how she once found a door. She convinced Trey to come with her and they somehow made it to the opening of a cave.
They find a forest sitting 80 feet in front of them and soon find themselves walking down the dirt trail. Trey thought this was insane and was baffled when they saw another world. Zoey quickly realized that it was not safe and they went to hiding in the trees.
After days of walking and getting farther and farther away from home, they come across the first city that was built after the destruction. They spent days leaning the truth and realizing that the congress knew the world was still populated.
After secretly contacting their family and friends, they set out on destroying the congress and saving everyone from the ground. They secretly got people on board and headed back to their home and destroy it.
Once they got back they saved everyone and blew up the underground city. Everyone made it to the city and started making a life for themselves. Life was going great until they all were walking down the street and a train came speeding down killing them all and life was then destroyed after all their hard work.