As the climate breaks down across the globe and inexplicable comets appear in the sky, artist Lyra Darkwood chats by hologram every night with her genius older sister, Arda. It's comforting. Arda is a world-renowned scientist. She'd know if anything were really wrong. Wouldn't she? But as time passes, the hologram starts to feel uncanny. Lyra finally comes to a horrifying realization: she's been talking to a deepfake for seven years. The ensuing search for the real Arda will take Lyra across oceans and continents and even to the virtual-reality depths of outer space, where she will encounter firsthand the terrible truth that sent her sister into hiding-and embark on a desperate mission to tell humanity of the coming danger.