January 1986. Fifteen-year-old Nick Hayes fights cancer. And every week, together with friends, he immerses himself in the world of the role-playing game Dungeons & Dragons to briefly escape death. One day Nick will meet a stranger who will reveal what will happen in the near future. Who is he— a mad maniac with otherworldly powers, or a time traveler? How do you survive in one of many realities and get around the laws of physics? And how can one choice decide everything?