I've been enjoying Luther, in much the same way I enjoy Spooks - it's nonsense, but it's fun to watch. Idris Elba is brilliant; it's hard to believe that he was Mr Super-Cool Stringer Bell in The Wire, so uncool and permanently about-to-lose-it is his character in this. My other favourite is Alice Morgan, cheerfully hammed up by Ruth Wilson. What TV copper wouldn't want an attractive evil female genius going round sorting out his problems for him, including his semi-ex wife's irritating lover (Paul McCann) and a child murderer who - until Alice's intervention - refuses to die? She's the original mad, bad and dangerous to know girl, but you can't help liking her.
While the plots have stuck to nicking villains (helped by Luther's trademark gimmick, psychological insight), Luther going round to punch holes in his ex's doors (in a loving, non-threatening way) and Alice going round threatening (or murdering) anyone who poses a threat to Luthie's happiness, it's all been fine. So what went wrong in this episode? Two things. First was the violence (even though we didn't actually see it) in what turned out to be the fairly throwaway central plot about the kidnap of a couple involved in diamond theft. They didn't need to cut her tongue out, especially at 9.10pm. Unfortunately that example of too much too soon was a harbinger of things to come.
No sooner had the tongue been removed than we learned, very suddenly, that Luther's sidekick DCI (the one who looks a bit like Ian Beale from EastEnders - and, to confuse things more, is called Ian) had been on the take all along, and was involved in the diamond sting. No warning, no subtle hints dropped in previous episodes, just bang - one minute he's a solid copper, the next he's visiting the chief crook and telling us that he's been happy to cream off a slice of villain-on-villain robberies all these years but draws the line at the tongue business.
This is plotting of the "OK and by the way Ian Beale has been a major league crack dealer all these years" variety - technically feasible, but so sudden and unforeshadowed that it renders any attempt to get 'into' the series completely pointless, because you don't know how they're going to arbitrarily redraw the characters and their relationships next. Plenty of coppers have been revealed as bent in TV shows, but the idea is that you give the audience some clues and let us work it out for ourselves, not just lob it in like a giant brick when you need the plot to take a 90-degree turn. It goes without saying, of course, that Luther's response to discovering his friend's villainy was absurd, with the normally voluble DCI keeping quiet about it long enough to end up framed for a murder which Ian had committed, thus bludgeoning us into a cliched (sorry - classic) season finale in which he's on the run from his own colleagues. At least he's (apparently) going to be helped by louche, homicidal nuclear physicist Alice, my favcourite new TV character of the year. I'll watch it for her, if nothing else.