Gabe keeps lists: why he's real, reasons he's not, and the rules that seem to dictate his strange existence. Danny says he's her imaginary friend and that's always been enough for the pair of them. But when she enters high school and a world of stress, turbulent emotions, and surprising first crushes, he finds himself asking questions and wanting things he never has before. His search for answers about where he comes from and why he's here becomes critical as Danny faces a profound personal loss and they both begin to understand growing up means sacrifice and learning truths you never wanted to know.