There's another Line of Duty theory doing the rounds that not only connects the dots between past series, but it could also lift the lid a bit further on that Jo Davidson cliffhanger from episode four. The crux of it boils down to deciphering precisely what Gail Vella had uncovered, ultimately leading to her murder by the OCG. The theory – which was first shared by Twitter user Eleanor Crossland – argues that Vella started digging into police recruitment, finding a disproportionate number of new officers coming from backgrounds in foster care. This spurred her to look back into the case of retired Chief Superintendent Patrick Fairbank. We already know, from Vella's broadcast footage in season six, that she covered the trial as it was unfolding, and that she had talked about links between the police and high-profile child abusers in her reports.