It's 2012. Agnetha Fältskog is working on a new album and is asked to write a song for it. She is still heartbroken over leaving her ex-husband, Björn Ulvaeus, nearly 40 years earlier and begins writing a song for him based on a little box that she keeps on the floor beside her bed. Meanwhile, Björn himself is working on projects of his own and is constantly thinking about Agnetha and is hoping to find ways to get him and Agnetha together again. Little do they know, that song will get them back together again.