And if there's one thing we know about Line of Duty, it's that it loves to keep us guessing in the time between episodes.
So who is this nominal, known to the police, who is a blood relative of Jo Davidson's? Many viewers seem convinced that it's John Corbett, from series 5.
Corbett is the biological son of Anne-Marie McGillis, an old informant to Ted Hastings in Northern Ireland. McGillis was killed by the IRA in 1989, at which point Corbett was sent to Liverpool to be raised by his aunt and uncle, hence the accent.
Corbett was killed off in series 5, when the OCG finally had enough of his nonsense and Ryan slit his throat. So he won't be coming back, but going by Hastings' reaction to Steve's revelation, and the photo of what appears to be Jo's mother in her bedroom, fans seem convinced he is Jo's brother.