Phoebe is a brilliant robotics engineer struggling to come to terms with the death of her younger sister, Edie. Defying all the protocols of the tech company she works for, Phoebe uses years of messages, videos and social media posts to create a lifelike AI replica of her sister, at first bringing her a great deal of joy and comfort. However, Phoebe's extraordinary invention soon forces her to confront one impossible question: if you could bring someone back, should you?