Hidden Agenda is the 1630th episode of The Bill.
As they enter Sun Hill, P.C. Hagen suggests to Sgt. Boyden that a short holiday might save their rocky relationship but he is adamant that it's over. Later, they are both part of a team watching the home of the Padfield brothers who are suspected transvestite-bashers. The police move in and as Boyden restrains one of the brothers he begins to caution him but does not complete it. Back at Sun Hill, P.C. Page finds Hagen crying in the locker room. She reveals that despite sleeping with Boyden last night their relationship now appears doomed. Page suggests she moves out for a while. When a witness to one of the assaults identifies the Padfields, CID are confident of getting a result. However, Padfield complains that he wasn't formally cautioned. Despite Boyden's insistence that he was, D.C.I. Meadows demands confirmation from his nearest colleague at the raid. Horrified, Boyden realises it was Hagen. Despite the urgings of Boyden, Meadows and Ch. Insp. Conway, Hagen refuses to vouch for Boyden. When a barman at the All In Bar is poisoned, the owner recognises one of the perpetrators as a cross-dresser. When Meadows and D.S. McAllister threaten to reveal his secret to his wife and the "concerned parent" group he belongs to, he confesses, and also implicates Padfield. Hagen makes a last ditch effort to salvage their relationship, but Boyden throws her out of his flat.