The year is 2019. Paul Melville has been in perfect love with Elsa for four years. It's a romance made of white threads since the two lovebirds met thanks to Osmosis, a program created by Paul's brother Thomas Melville, which helps its users find their soul mate by evaluating their compatibility. The algorithm is richly fed by the "datas" of individuals, constantly connected, constantly interacting, who share on social networks as they breathe. But one day, while Paul is testing his brother's latest invention, he is thrown back into his past, or maybe it's just a memory? Elizabeth is there. The one he was madly in love with before Osmosis came into his life. She had disappeared overnight, and Paul remembers. He decides to investigate and is approached by the enigmatic Harmony.