Ted Hastings and his AC-12 crew are interested in one thing, and one thing only.
But do you know what it is?
We've got a super-tricky Line of Duty quiz here for you to get your teeth into ahead of this weekend's episode – the penultimate in the current series.
As first reported by Wales Online, it'll test everything from your memory of those famous interrogation scenes, to the array of crooked characters to have graced our screens, and crossed paths with Kate Fleming, Steve Arnott and Hastings (like the Battle) in recent years.
So do you know your CHIS from your SIO? Your Dot Cottan from your John Corbett?
And how closely have you been paying attention in the pursuit of the ever-elusive H?
12 testing questions can be tackled in the quiz below.
Warning - there may be some spoilers!
Remember to let us know how you got on by sharing your score in the comments below this article or on social media.
