Seventeen-year-old Oliver Mc'Neil has never been outside. Like everyone else in the Fifth City in the year 2085, he and his mother live in an apartment where the air and water are sterile, their food is couriered to them, and all their activities are done indoors on sims, machines that simulate life using computer monitors, virtual reality headsets, and holograms.

When Oliver wakes up in the middle of the woods drugged and delirious, he has no idea how he got there, but he is certain it is a death sentence. He is taken in by the rugged and beautiful Autumn, whose family is loud, rambunctious, and three children over the legal birth limit. They are outlaws, living with thousands of others in a network of underground caves, where modern technology is forbidden and secrecy is paramount. Oliver must learn to survive in a land that is wild and dangerous, while battling voices in his head that haunt him day and night. He doesn't know if the hallucinations are due to withdrawals from the mind-numbing medication he has taken every day of his life, or if he truly is the monster he appears to be. One thing he is certain of: he will do whatever it takes to protect Autumn, the girl who saved his life.

Cave sentries begin to go missing, leading to a series of disasters and growing suspicion about Oliver's appearance in the caves. Now his choices will either save or endanger his friends. Will he ever be able to trust himself in this strange new life?