In the 1970s, a music promoter discovers conjoined twins Tom and Barry Howe (Luke and Harry Treadaway) and grooms them into a freakish rock act. Gifted with enough talent and drive to parlay their band into a proto-punk sensation, the twins move beyond their sideshow roots. But darkness hangs over them, as they engage in jealous battles over their shared lover and deal with a dormant but sinister third head growing out of Barry's left shoulder.