SINCE Thirteen Steps Down is based on a novel by Ruth Rendell, whose work provided the bedrock of ITV's crime dramas throughout the 1990s, there are a few mysteries to be cleared up.

Is that really the ghost of serial killer John Christie, of 10 Rillington Place infamy, haunting disturbed protagonist Michael 'Mix' Cellini (Luke Treadaway) or is Mix just, well, a bit mixed up in the head?

Why is Mix's cranky spinster landlady Ms Chawcer (62-year-old Geraldine James in unflattering oldie makeup) so intent on finding the recently widowed doctor who was her first love, and what were she and a young girl doing visiting Christie's house way back in the day?

These and other questions will, I imagine, be answered in next week's concluding part.

In the meantime, the big head-scratcher is how a book by Rendell, who's revered by readers, critics and fellow authors as the mistress of the psychological thriller, could be turned into something so silly, unconvincing and hysterically over the top as this.

Mix's twin obsessions are Christie, who murdered at least eight women in the 1940s and 50s and who used to live in the next street, and a famous model called Nerissa (Elarica Gallacher), who he's been stalking.

Nerissa is aware of Mix's creepy behaviour but appears to treat it as some kind of diverting cat-and-mouse game, which raises another question: how come, in this day and age, a famous model doesn't have some security muscle to protect her as she wanders around London, curiously unrecognised by everyone, except Mix?

But, anyway. Mix, who works as a gym equipment repairman, isn't exactly a loner. He's having regular sex with a married, moneyed woman who summons him to service her treadmill (arf, arf!) while her husband is away making her even richer.

As a way of getting closer to Nerissa, Mix effortlessly picks up and beds the pretty but vacuous Danila (Victoria Bewick), who works as a minimum-wage slave at the elite health club the model frequents.

Mix's indefinable appeal to women is perhaps the deepest mystery of all. Frankly, he couldn't be any creepier if he had "I am a nutter" carved into his forehead in blood-red tattoo ink. Poor, dumb Danila doesn't even smell a rat when Mix admits that he once tried to brain his baby half-sister with a bottle of tomato ketchup. When Danila takes a peek at Mix's intimate diary and then accidentally breaks the picture of Nerissa he keeps on his mantelpiece, he bashes her head in with a flashlight and hides her body under the floorboards -- just as Christie did with his own wife.

Thirteen Steps Down is thoroughly daft stuff, although well acted. I'll probably watch it next week, if only for a few more glimpses of Dublin, where much of it was filmed.

Postponed in June due to legal issues which have now been resolved, The Riots: In Their Own Words is a two-part quest to find out why London erupted into violence and looting in the summer of last year.

This episode, which dealt with the rioters' side of the story, eschewed traditional documentary techniques in favour of having actors speak the words of people who were interviewed for a project called Reading the Riots, organised by The Guardian newspaper and the London School of Economics.

It was a needless piece of fussiness that erected an artificial barrier between the viewer and what was being said. Not that what was being said was conclusive.

"It was like Demolition Man [a Sly Stallone movie]," said one male 'rioter'. "There's a higher class and a lower class, and we're in the lower class. That day we had the power."

A young girl's explanation for becoming involved was simpler, and perhaps more honest: "I'm getting all this free stuff and I'm not gonna get caught, 'cos everybody's doing it."