The drama is adapted from the best-selling science fiction series of the same name by Hugh Howey. The story takes place in a dystopian future where about 10,000 humans live in a silo-type bunker 144 stories deep. They are told that the outside world has become unsuitable for human habitation due to poison gas infection. The remaining survivors then take refuge in the bunker and formulate rules to maintain the operation of the new society in the bunker.