Leeds police constable Jo Gillespie (Sheridan Smith) is devastated when her husband, undercover officer Ryan (Kenny Doughty), is killed in suspicious circumstances. As she battles to stay strong for the benefit of daughter Melly (Honor Kneafsey) and stepson Hal (Oliver Woollford), Jo is urged by her bosses, DCI Will Hepburn (Douglas Henshall) and Chief Constable Carolyn Jarecki..