"Abbafab", the hugely popular Abba tribute band, are in trouble. Gemma Redden 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. But 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 older sisters, Gemma and Wendy.
Meanwhile, Mia's oldest friend, Alva Ryan, is having a life crisis of her own, Her builder boyfriend and all-round-good-guy, Sean Malone, has just walked out and this time he swears he's not coming back. And Alva's sister, Kerry, is having rather unusual problems of her own.
Things come to a head when Wendy has a terrible accident, because she is harbouring a secret that could blow the band apart and devastate the close bond of the Redden sisters. But secrets have a way of coming out when you least expect them to.