It has been almost seven years since we were last up Ripponden, in the BBC drama Happy Valley, and to judge by the reception this week, you’d have thought it a return to paradise. As with the first two seasons, the opening episode of season three was a pitch-perfect combination of family and police drama. It was also a continuation of a set of incredibly grim themes that have brought us peculiar joy: in addition to the suicide, rape and murder of the first two seasons, here comes addiction, coercive control and another slightly rapey guy – not quite in the league of Tommy Lee Royce, but definitely not someone you would want to be married to. The appeal of bleak things drives a large portion of the entertainment industry, but where Happy Valley thrives is in the refuge it offers from its own horror. A lot of this has to do with the warmth of the relationship between sergeant Catherine Cawood, played by Sarah Lancashire, and Siobhan Finneran as her sister Clare, two actors of such extraordinary ability that you could strip out all the drama and pass a perfectly enjoyable hour watching them chat over tea. As it is, the juxtaposition of their humanity and banter with the most hideous of storylines brings about a joy right up there with losing and then finding your wallet. Part of the wildness of the praise attending the first episode this week – “stronger than ever” (Radio Times), “television’s greatest saga” (the Independent), “doesn’t get better than this” (the Telegraph) – is a simple case of relief. Most of us have been through the small but real letdown of watching a favourite TV show fall off a cliff. Season two of Big Little Lies was self-conscious to the point of parody. The last season of Line of Duty was a pale imitation of the original shows. Another of Sally Wainwright’s franchises, Gentleman Jack, was dropped last year by HBO after failing to find its feet. What if – real-life horror! – Happy Valley wasn’t as good as we thought it had been? Or, in the years since season two, had been outstripped by better shows? We needn’t have worried. The pleasures of this very specific set of characters were there from the start, as was the deep satisfaction of returning to a well-built fictional world. Royce is a villain of the first order, but Wainwright’s greater skill, perhaps, is in creating the nebbishy guy whose small-time crookery spins out of control, sucking in his oblivious family. A certain type of weak man has been a trope of Wainwright’s since At Home With the Braithwaites, and so it was this week in Happy Valley, when a local pharmacist-turned-drug dealer wanders almost immediately out of his depth into the jaws of much bigger criminals. If it’s a combination of genres – the soothing rhythm of smalltown cops and concerns with the grisly realism of a big-city drama, or Last of the Summer Wine meets The Wire – it works to an unusual degree. And one forgets how funny the show is. There’s an entire comic interlude in which Cawood tells her sister to do one at the suggestion she take up yoga after retirement. For those watching in the US, there is the added amusement – seven years later, I’m still laughing at the memory of this from season two – of trying to get Americans to pronounce “Sowerby Bridge” or decode the phrase “down at cafe that does us butties”. (When I ran this by an American in 2016, he looked fleetingly panicked before grabbing wildly on to the word “butt” and suggesting: “Is it something to do with his ass?”) For all these comforts and thrills, the greatest delights of Happy Valley are, for me, the scenes in which Lancashire sizes up some horrible man – in this case, a sadistic PE teacher – who five episodes hence, we know, will get his comeuppance. Anticipation of future revenge; the cool assessment of a character who thinks his nature is fully concealed; the grumpiness of a heroine enraged at the mere suggestion someone might throw her a retirement do; and the sheer acting skill of Lancashire, whose face hits shades of incredulity that seem to expand the range of human expression. It’s hard to think of a better way to spend January. Emma Brockes is a Guardian columnist