Smitty and Tara live on Tube World - it is all they have ever known. They imagine that getting married and having babies will be their greatest adventure. But they couldn't be more wrong. Smitty has inherited more than a parabike from his Uncle Elmo. He has inherited a code which will open a whole new future for them and for all the ten thousand Tube Dwellers who share their world. By exploring the hidden spaces accessed by the code, Smitty and Tara are bravely flying in the face of laws enforced by the Tube World Council - which encourages its people to live, work, and think in a strictly regulated fashion. But the clock is ticking and Tube World can't sustain life forever. Their bravery means that Tube Dwellers have a whole new future to look forward to - a second chance on New Earth.

But preparing for a flight to a new planet, and actually building a life there, will be fraught with untold dangers and challenges for Smitty, Tara and their friends - not least from those who already populate the new world.