Leeds police constable Jo Gillespie is devastated when her husband, undercover officer Ryan, is killed in suspicious circumstances. As she battles to stay strong for the benefit of daughter Melly and stepson Hal, Jo is urged by her bosses, DCI Will Hepburn and Chief Constable Carolyn Jarecki, to leave it to her fellow officers to find the killer. But when the murder inquiry starts to uncover some dangerous secrets about Ryan, Jo's faith in the police family of which she has been a part for so long is severely tested. No longer sure who to trust, Jo embarks on her own investigation with the help of friend and colleague Jack Clark, but as they close in on the identity of Ryan's killer, Jo's hunt for the truth will put her own life in danger.