In the Run, oxygen is not free. Your lungs do not belong to you, nor do your legs, nor the walls that keep you in. They belong to the 'Birds' up on Velimore, where there is light and colour and air, where you do not have to run, where you are not the dregs of society and you have control, respect. But beneath, you produce what the Birds need to thrive: energy. As the world around Klaod starts to collapse, can the Runners find a way to live?