ABBA's story seems never to end. The band members met 50 years ago, and had an extraordinary run of success. 20 years ago the musical Mamma Mia! premiered in the West End where it is still running, and has been seen by audiences on Broadway and round the world. Add two movies, Mamma Mia! The Party opening at the O2 in 2019 and a forthcoming tour with ABBA members played by holograms, and ABBA goes on forever. This documentary tells that story.