It is a weekend of season and series finales. If you care, it’s the season finale of 'Madam Secretary' (Sunday, CBS, Global, 8 p.m.) and 'Elementary' (Sunday, CBS, Global, 10 p.m.). And it is the series finale of 'The Good Wife' (Sunday, CBS, Global, 9 p.m.) The latter will be much missed and it’s worth noting that when it began seven seasons ago it was rare to find a network drama anchored in one female lead character.

Of even more significance to many is what is probably the final season of 'Wallander' (Sunday, PBS’s Masterpiece Mystery!, 9 p.m.). I say “probably” because star Kenneth Branagh has hinted that he doesn’t want to fully let go of the character and there might be a Henning Mankell short story that can be adapted in the future. Still, it is likely that this batch of Wallander mysteries is the end of it and anything else will be an addendum.

The first of the new batch, 'The White Lioness', is a disconcerting experience to begin with. Certainly to anyone familiar with the TV series rather than the novels.

The brooding, laconic Swedish detective Kurt Wallander is not in his native Sweden. We do not have the Swedish weather to telegraph and illuminate the shifting mood of the mystery story. He is in South Africa, giving a talk at a conference, and becomes involved in the case of a Swedish woman who has disappeared there. The viewer is pretty sure from the start that she’s dead.

But Wallander pokes around, and is often out of his depth in the local politics and social customs. While it lacks the Swedish atmosphere, it is visually arresting, as always. Mankell’s Wallander novels always have cold, despairing heart and that sensibility certainly isn’t missing, even in the vast, hot and dry scrublands of the new setting.

At first it seems that Wallander has found some peace in his life. He’s older now, a distinguished veteran – that’s why he’s invited to South Africa – and he looks ruefully, but without regret, at a group of other cops boozing the night away in his hotel. The drama takes a diversion from the original novel but it keeps the essence of the plot intact – someone is plotting to bring chaos to the country as a sort-of revenge for the end of apartheid and arrival of black rule. And financial corruption is the easiest route to that.

As ever, Branagh’s Wallander is all surface reticence and gravity, but under that there is a stew of anger at the state of the world and a despairing feeling of old age creeping into his bones, his soul. Branagh is remarkable in the role. He was from the start but now he is obviously relishing the aging Wallander’s doubts and frailty. A glance, a mere shrug from Branagh and we see Kurt Wallander’s years of pain and contrition exposed. Branagh has said that he finds it hard to wash away the character after spending months filming, and it’s easy to see why – he has so much invested in this role and it feels like he was born to play him.

In later episodes, the mood and tone shift back, closer to the Nordic noir that Mankell’s work helped create and that the first Wallander TV mysteries starring Branagh helped establish. Back in Sweden, the detective is feeling frighteningly dilapidated and vulnerable. Such is the depth of the character in weakened near-retirement and such is Branagh’s immersive exploration of him that, in truth, the series transcends the Nordic noir genre. It’s about an exhausted man fearing all the ailments, mental and physical, of old age.

Branagh is 55 now and from the start was a little young to play the character. But by heavens it works. His voice is low but it carries. He commands the series with something immeasurable – one sees a short, slightly stocky man, grey-haired and almost always with a day's growth of grey stubble on his face, making him look a little ordinary, a harried man on a work deadline.

But the charisma and skill, the immeasurable things, make this series breathtaking to watch.