You never stop being an addict. To overcome addiction is to be in a state of permanent recovery from it. So when Kieron pours himself a glass of water and refers to being an alcoholic in the past tense, you know it’s only a matter of time before he’ll relapse. And sure enough he does – in an inevitable scene where a marvellous Stephen Mackintosh silently moves through the gears of temptation before losing a staring competition with a pint of beer – and all while inadvertently helping Michael indulge in his own habit of pursuing his old teacher Mr Sellers.

The more Michael finds out about Mr Sellers and why he’s hiding Elizabeth Fletcher, the more he becomes entangled in a life that isn’t his, to the point where he’s eating someone else’s bacon and smooching people who aren’t his pregnant wife. As he kisses Elizabeth like the rebellious randy teen he once was you realise that he can’t seem to leave the emotions of his teenage years behind. It’s as if he’s fixated with stirring up history. His own and those of others.

But then that’s what What Remains is all about: walking over the hot embers of the past and trying to hide wincing at the pain from everyone else, especially if it’s a greyed ex-detective. It’s an exercise in emotional archaeology, and this week the further remains of Melissa Young’s life are uncovered.

Before she went for a long lie down in the loft, Melissa wasn’t quite the loner we all thought; having had an uncomfortable co-dependent relationship with a perpetually drink-drenched Kieron. You don’t know whether to feel sorry for her or frustrated, as you watch her put up with someone else’s dependency while trying to cure her own cravings for comfort eating.

Even Len can’t give up. The habit of being a copper and the addiction to justice runs so strong through him and his leather jacket. The frustration wrought on his face as he realises he has no grounds to arrest teenage dirtbag Adam, and breaks off the recitation of this rights is so pained you’d have thought he was sawing through his own forearm with his teeth. David Threlfall has been, and continues to be, a demonstration of consummate talent, and we look forward to whatever he appears in next, sad though we’ll be to see the back of him and the show next week.

We’ve become rather addicted to What Remains, and it’s a shame our Sunday night fix is about to be snatched away from us. This time next week you’ll know who the murderer is. So it’s place-yer-bets time people – winner gets a chunk of that rotten pineapple from Episode 1.

Aired at 9pm on Sunday 8 September 2013 on BBC One.

> Order What Remains on DVD on Amazon.

Watch the trailer…

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