Last Night's TV: Coming Up: I Don't Care/Channel 4<br />Mistresses/BBC1

Thank goodness for Coming Up. A collection of short films from Channel 4, it offers young talent a chance to show their skills with a brief slot on Thursday night. It's not just a break from the monotony of the channel's hospital/police office/chat-room-heavy roster; it's a genuinely interesting display of possibilities.

Last night's drama, I Don't Care, was a rather peculiar little look inside the life of Luka Bartholomew. Full-time carer for his mother, he inhabited the kind of lonely, anonymous rotation that dominates so many lives: corner shop, sea front, kitchen, bedroom. It didn't help, of course, that his particular corner shop, sea front, kitchen and bedroom were situated in Porthpunnet, a tumbleweed retirement community, all "candy floss and grey skies" as he rather poetically put it.

The day we caught him also happened to be his birthday, an occasion his mother had – poignantly – decided to mark by bringing in "a woman". "Who's that?" asked Luka, bewildered on hearing a feminine voice echoing through the house. "Your birthday present," announced his mother. Luka's initial horrified assumption was rather unsavoury: "You got me a woman?" came the bemused reply. Of course she hadn't: she had got him a day off.

It was a curious concept. Luka, habituated to a life of relative entrapment, found himself with 12 precious hours. Twelve hours not to cook, clean or care, but to do precisely what he wanted, when he wanted. Except that he didn't. As fate would have it, all trains out of Porthpunnet were cancelled. We found out moments later – through a passing conversation with a stranger in a cafe – that it also happened to be Sunday. Nothing, Luka assured the stranger, is open on Sunday.

The only thing that was open was the aforementioned corner shop, where we found – of all things – Paloma Faith, the pseudo-kooky popstrell of recent chart success, serving behind the counter. Done up in trademark red hair and lips, she presented a rather incongruous figure. I have to say, I don't think this worked: had her character turned out to hold some mystical power over Luka, to be the girl whose worldly ways would open his eyes, it might have. As it happened, her role was fleeting and incidental: a bottle of sherry bought here, a fight broken up there. She was as much a small-town figure as he, and a slightly implausible one at that (she isn't, however, a bad actress).

Indeed, the life-changing encounter came courtesy of Dan, a brittle, coked-up nomad. Lairy and extra-volumed before he had even got truly smashed – which he did with a malleable Luka – he entranced his parochial new friend with tales of his travels. Their whirlwind romance (for that was what, broadly speaking, it was, whether Luka was aware of it or not) rapidly turned sour. The pair parted bloody and embittered, Dan driving off into the sunset, leaving Luka to return to monotony.

Except that Luka decided to leave. Poignantly, he returned to give his mother a note; at home he was greeted by a birthday cake. Still, he went, coming-of-age complete.

The thing is, it was difficult to empathise with this decision. Luka was a rather detached character who wore a look of baffled incomprehension for much of the drama. He did not tug at the heart strings. His mother, on the other hand, offered the only real display of human kindness of the whole programme. She was going to wake, presumably, to find an untouched cake and an untouching farewell. This bleakness was no doubt intended, but it would be that much better if the audience was convinced by Luka's likeability. Then we, like him, would have been torn between his two fates.

Part of the problem may have been in the length of the programme. It was very short indeed: only half an hour. It was a shame, since we could have used some extra time to delve properly into Luka's soul. At least, though, the curtness of our encounter left us wanting more; far better that way than the other.

As we glided into the third instalment of what is very likely (and sadly) to be Mistresses' swansong, the gaiety of last week's episode was long gone. Series three, part three was very much in the sombre mode that has been so heavily trailed. Jessica was feeling isolated, by her embarrassment at her chaotic domestic life as much as by a sighting of her friends gathered, without her, around a drink. Siobhan, meanwhile, suddenly found herself the sensible, stoic denier of Dominic's affections, a role no doubt bolstered by the attentions of a good-looking photographer (stubbled, bescarved, in classic Television Artiste mode). Trudi and Katie were still entangled in Trudi's wobbly marriage, one that doesn't look likely to last much longer if yesterday's grim finale was anything to go by. It wasn't the fluff that fans love, though it wasn't terribly lacking without it. Things are starting to fall apart for our heroines, and, in many ways, it's rather nice to see them coping. Usually so easily swayed, so tempted, so naughty, the foursome proved as strong as they have been feisty, a notable improvement on the soppy starlets who occupy the programme's sibling shows: Sex and the City, Desperate Housewives et al. Mistresses may have taken a turn for the darker, but it is far from a turn for the worse.