Lots of things designed to be used by children end up appealing to adults too. Harry Potter. Jelly babies. The list is endless.

TV's Doctor Who is a good example. Originally conceived as an educational drama for 1960s kiddywinks, it attracted a devoted adult audience from the very beginning. They knew they were watching something that wasn't, strictly speaking, "for them" but they loved it anyway.

The trouble with Who's freshly-minted anagrammatic "sister" serial Torchwood (Sun, 10pm, BBC3; Wed, 9pm, BBC2) is that it's not really clear who it's aimed at. It contains swearing, blood and sex, yet still somehow feels like a children's programme. Thirteen-year-olds should love it; anyone else is likely to be more than a little confused. Which isn't to say Torchwood is bad. Just bewildering. And very, very silly.

The central presence of Captain Jack Harkness, one of the most pantomime characters ever to appear in Doctor Who, doesn't exactly help. He's like Buzz Lightyear, but less realistic. The moment you see him running around being all larger-than-life, you think "aha - so Torchwood's a camp space opera? Fair enough".

But then the storyline goes all dark and unpleasant and people are getting their throats torn open and shooting themselves in the head, and suddenly you don't know where you are. Not in Kansas anymore, maybe - but where?

Cute and dark, sweet and sour, up and down. It's like tuning in to watch Deadwood, only to discover they've replaced Al Swearengen with the Honey Monster. Or sitting through a "re-imagining" of the Captain Birds Eye commercials, in which the white-haired skipper traverses the oceans in a raging thunderstorm, ruling his child-crew with an iron fist, tossing dissenters overboard into the rolling, foaming waves - but dances the hornpipe with a big cartoon haddock while the credits roll. Or stumbling across an episode of Scooby-Doo in which Shaggy skins up on camera.

In fact Scooby-Doo (more than, say, the X-Files or Buffy) is probably the show most analogous to Torchwood, in that both series revolve around a fresh-faced team of meddling kids tackling an ever-shifting carnival of monsters in a world of childlike simplicity. The Torchwood gang even have their own version of The Mystery Machine, although theirs is a spectacularly ugly SUV with two daft strips of throbbing LED lights either side of the windscreen whose sole purpose is to make the entire vehicle look outrageously silly - they might as well have stuck a big inflatable dick on the bonnet, to be honest.

The inside's not much better - LCD screens embedded in every available flat surface, each urgently displaying a wibbly-wobbly screensaver ... it must be like driving around in a flagship branch of PC World.

There are other glaringly daft touches: the countless overhead helicopter shots of Cardiff (what is this, Google Earth?); the ridiculous severed hand-in-a-jar (straight from the Addams Family); the protracted sequence from episode one in which Captain Jack stood atop a tall building surveying the cityscape like Batman FOR NO REASON WHATSOEVER. Oh, and the team's insistence on using the silly invisible elevator that slowly, slowly ascends through a sort of "magic hole" in the pavement - even though there's a perfectly reasonable BACK DOOR through which they can enter and leave the Batcave at will.

And on top of all that, there's a bizarre emphasis on bisexual tension thrown in for good measure. You half expect the Torchwood gang to drop their slacks and form a humping great daisy chain any moment. It's Shortbus meets Goober and the Ghost Chasers meets X-Men meets Angel meets The Tomorrow People meets Spooks meets Oh God I Give Up.

Still, the act of jotting down some of Torchwood's thundering absurdities has put a big dumb smile on my face. Whatever the hell it's supposed to be, there's nothing else like Torchwood on TV at the moment, and that's got to be worth something. I just don't have a clue how much.