Last night's viewing - The Fall, BBC2; The Flying Archaeologist, BBC4

"No one knows what's going on in someone else's mind and life would be intolerable if we did," murmurs Paul to his wife soothingly. Paul knows what he's talking about. He's a therapist and bereavement counsellor and, apparently, a loving father, currently a little preoccupied, like his wife, by his daughter's recurrent nightmares. In fact, the two of them are in her bed, the little girl having been resettled in the parental room after waking up screaming.

But Paul's general observation has a sharp personal resonance too. Like him, we're aware that his wife's hand is just an inch away from the psychopathic journal he's hastily concealed beneath the pillow. And this isn't something he's brought back from the office. It's all his own work.

It was a nice moment in Alan Cubitt's new Belfast-set thriller, The Fall, or at least nicely creepy, which is one of the things we ask for from a serial-killer drama. And it underlined one of the central twists in this addition to a frankly overcrowded genre. We know who did it from the opening minutes, and we know he's a killer before we discover the far more unsettling information – in the context of our genre expectations – that he's a gentle daddy. Weirdos in hoods who prowl around women's bedrooms fingering their underwear are two a penny in television crime. Weirdos who then go home and give their little boy a cuddle because he's woken in the night and is frightened are a good deal less common.

But then The Fall is interestingly skewed from the beginning. How many times has the camera stalked a woman moving around her bathroom as the prelude to fictional gynocide? How many times, though, does it turn out to be the detective not the victim; in this case, Gillian Anderson at her most dressed-down, with a face-pack on and cleaning the tide-mark off the bath.

It lasts a long time, that studiously downbeat beginning, and then, just as you're wondering what you're meant to make of domesticity this drab, there's an unsettling echo: the film cuts to another bathroom and a figure in black pottering far less innocently, just the first of several pointed connections between the killer and the woman who will end up looking for him.

They're connected by psychology too, a combination of control and transgressive impulse. As Stella Gibson, a Metropolitan police officer brought in to review a stalled murder investigation, Anderson is all icy reserve. Climbing into the hotel swimming pool she puts on her goggles as if she's assembling a watch. But she keeps a journal too, a record of dreams that seem to come from a far less ordered place than the crisp white blouse and clipped diction. The killer, meanwhile, can still the murderous rage in a grief-stricken father but do nothing with the compulsion that is driving him to repeat his crime.

There is a political subplot brewing up – with a corrupt Unionist politician leaning on the conduct of the investigation – and (because I was sufficiently gripped to look ahead at episode two) an eruption of violence in a direction you haven't suspected. But for the moment, the heart of the thing is in the enigma of two minds, both predators of a kind, both prey to compulsions and both gratifyingly more complicated than the stock types we're conventionally given. It seems a pity that, yet again, attractive young women have to be sacrificed for public entertainment. But at least the entertainment is more thoughtful than usual.

In The Flying Archaeologist, Ben Robinson took to the skies over Hadrian's Wall to share recent archaeological findings that are "rewriting history". Bullet-point revelation? The wall wasn't a demarcation between wilderness and semi-civilisation – a real life equivalent to the northern border in Game of Thrones – but a fortification with prosperity and settlement on both sides of it. Think Catterick, with togas and goatskin tents.