As we embark on series six, a far greater problem is the weight of the past. As the plot races on, names and events float to the surface of my consciousness like something disturbing in a canal.
I have hopes for Macdonald as the most intriguing villain yet. The acting, the facial hints of a double, if not triple, life, subtle, that ageless face able to morph from tender to slab-cold cruel within an eyebrow.
Line of Duty has been a smash for lots of reasons. The tight as a tourniquet plotting. The sensational twists. The slick editing. But at its heart are the three main characters, the little family against the machine.
The first episode of series six returns to what Line of Duty does best: dodgy coppers, tense action and characters who communicate almost exclusively in acronyms.
In the best way, it recalled the first episode of the show's superlative second series: could Macdonald's intriguing, softly-spoken Davidson become an anti-hero to rival Keeley Hawes' Lindsay Denton?
Newbies to Duty may find it takes a little while to learn the lingo, but persevere, and you'll find cracking drama amongst the seemingly scrupulous attention to detail.
There is great potential here but last night's episode was at times impenetrable, as if taking our loyalties for granted. If I had been watching for the first time I might have switched off.
