Are you a good sister? AbbaFab, the hugely popular Abba tribute band, are in trouble. Gemma Redden, aka Agnetha, has just broken her ankle and finding a new singer to fill her white platform boots at such late notice isn’t going to be easy. Desperate times call for desperate measures and the youngest Redden sister, Mia, reluctantly agrees to don the blonde wig and sky-blue hot pants. For Mia, a shy piano teacher who has felt third best all her life, this is her big chance to prove herself to her two big sisters, Wendy and Gemma.