Greta is a young woman who has always lived with the thought that her sole purpose in life was to save her older sister Lucy. Greta was born so that her stem cells could be used to treat Lucy's leukemia. When Lucy passes away despite everything, Greta falls into a deep, existential hole. She has never left her hometown in Nebraska and has no idea who she is without her sister. Before her death, however, Lucy leaves behind a special, handmade game. This game forces Greta, guided by tasks and clues, to confront her grief and venture out into the world. The most important rule? She must play the game together with Will Tucker, a mysterious, introverted stranger who also turns out to have a mysterious bond with Lucy.