There's a society, led by the most unworthy person - Kim Namjoon's father - Kim Jacheol.
He knows that his own creation of society is cracking, bursting open at the seams. 
He and his son, among others, are part of a social class known as Highers.
However, those who do not belong in Higher, are sent away and are known as Unders.
The Unders are not satisfied with this cruel, biased hierarchy. They want a change - a big one.
They think they're on their own, but they can't underestimate the power of the social outcasts, those who do not fit into either tier, those who live in Purgatory, otherwise known as Broken.
Unders and Broken have more in common than they once thought, and they need to compromise to be able to work together to achieve the seemingly impossible.
Could blood relatives more important than success?
Could their ambition override teamwork?
Could they overthrow Higher?