The lives of four singers are far from harmonious. Danny's marriage is on the rocks, while Vince is struggling with a debilitating illness. Henry is having a mid-life crisis, and Neil is at war with his father. But when they sing together none of that matters. Because something magical happens. On a mission to compete against the best quartet singers in Britain, they turn to veteran entertainer, Ken, who inspires them to discover a curious vocal technique called The Fifth Voice. Over the course of a year and several adventures, they make discoveries about the power of music and friendship that help each of them shape the rest of their lives. And when they eventually find The Fifth Voice, they discover a prize much greater than the one they imagined.