Television: Ashes to Ashes, Friday, BBC1, 9pm

She was shot and then she was in the 1980s; she had some adventures with scary Bowie-clowns and frizzy perms and some awkward flirtation with the Gene Genie, and then she was shot again and was in 2010. The 1980s-world was a coma, but it seemed more real than the real world, she says.

In the present day, Alex Drake has normal hair and a psychiatrist, who tells her it was an illusion. She's seeing Gene and his gang everywhere, on TV screens, on DVD covers (but not, funnily enough, on Ashes To Ashes box sets), talking to her, telling her to wake up. Sweet dreams are made of this, says the soundtrack, still Now That's What I Call Music vols 1-16 on repeat.

Basically, this last run of Ashes To Ashes is the last ten minutes of Life On Mars stretched out for a series – and this time we're promised answers about what was really going on in both shows.

But what of Molly, the daughter that Alex has been trying desperately to return to for the previous two series? She's been sent off somewhere, we're briskly informed, which seems odd (a scheduling conflict or growth spurt for the young actress, perhaps?), especially when Alex slips back into the 1980s and quickly resumes her recitations of: "I'll get back to you Molly, I promise!" She didn't seem so bothered when she was actually in the same timezone as her … unless, of course, she wasn't really there. Or was she? I'm confused. As she says in the new intro: "My name is Alex Drake … and quite frankly, your guess is as good as mine."

The producers and writers of Ashes To Ashes have an almost impossible task with these last eight episodes. They've got to wrap up not only this story but that of the previous series, which ended – it's now clear – prematurely due to John Simm's wish to move on from the role. There's some grand narrative behind it all, apparently, a coherent explanation for Gene Hunt and his pals. I wonder, though, if it's really necessary. The appeal of LOM and then ATA – though the latter has been less popular, perhaps due to the original fans not identifying with the new setting, or perhaps because they brought in a girl to disrupt the laddish banter – has never really been the sci-fi element or the overarching premise. Though it's what TV executives call a high-concept show, the concept wasn't so much time-travel as an excuse to revive old-school cop show antics; first The Sweeney, then, well, TJ Hooker.

Does anyone really care what Gene Hunt is? Whether he's a fellow time-traveller, a manifestation of Fate or an actual genie isn't really the point, surely. And, in fact, tying him down too firmly to what might be an unsatisfying explanation could potentially ruin the character in future memories.

Well, they've decided to go for it anyway. There's an interesting speech in this episode by Daniel Mays as new character DCI Jim Keats, yet another tenuous authority figure trying to investigate or undermine Hunt from within the force. Keats seems to be trying to convince us that our Gene isn't the hero we've thought he was – apart from all the sexism and racism and police brutality, that is – but is actually the villain of the piece. I'm not buying it – I don't think that after five series we'll end up discovering that Hunt's the bad guy, or anything other than the man behind the curtain, blustering publicly while pulling some secret strings.

The plot of the week, about a kidnapped girl, is, as ever, dull and obvious. Sure, it's meant to be, but after all these episodes, it's becoming tedious to have to sit through these easily solvable cases, even knowing that they may well be the imaginings of a coma patient, in what's surely the most massive cop-out of any cop show.

There is another, more complicated kidnap at the heart of Blood And Oil, an interesting (and expensive) drama which is one of the BBC's big spring offerings. Set mostly in Nigeria, it has a terrific cast – Naomie Harris, Jodhi May, Paterson Joseph, Peter Firth, David Oyelowo – and an urgent subject, told through the structure of a thriller. May plays a British woman whose oil company worker husband is kidnapped in the unstable Delta region of Nigeria, where the industry is both the source of great wealth but also conflict. Militant groups protest the bleeding of their land, with accompanying pollution, by foreign companies and kidnapping to fund their activities is rife.

But the wife, Claire, and her accompanying minder, a helpful PR woman called Alice (Harris), find that there's a lot more going on when they get embroiled themselves. The thriller aspect may come off as a bit contrived, but it's a dramatic tale, shot beautifully and with fine performances.

More contrived, though, is the story of Canoe Man, with a faked death, escape to Panama and amnesia – but, of course, it's all true, as this is a dramatisation of the extraordinary story of John and Anne Darwin's deception.

I suspect this isn't the last time their tale will be filmed – surely Holly-wood is on it – but though this attempt suffers from a low budget and emphasises the odd domesticity of it all, Bernard Hill and Saskia Reeves (in a horribly unflattering wig) have a lot of fun as the inept, unlikely criminals.

Ashes To Ashes

Friday, BBC1, 9pm

Blood And Oil

Monday, Tuesday, BBC2, 9pm

Canoe Man

Wednesday, BBC 4, 9pm

• This Article was first published in The Scotsman on Saturday March 27, 2010