Underneath What:Steeltown Murders.

Badfinger tribute bands in smoky pubs where unreconstructed men drink pints with handles, kipper ties, vests, collars that could take your eye out, fish fingers, siderburns, Reliant Robins, Austin 1100s, rugby, and brown. So much brown. Brown leather jackets, brown shoes, brown cars, brown office furniture, brown curtains. Even the skies are kind of brown. Steeltown Murders (BBC1/iPlayer, written by Ed Whitmore and directed by Marc Evans) is filmed with a covering of sepia so dense (especially when the action goes back to the 1970s) that there's almost a hauntological vibe to the whole thing.

By the end you'll feel as if you've just listened to The Caretaker's entire haunted ballroom trilogy. But, at the same time, you'll have been treated to a hugely compelling, addictive, and, sometimes - often when you least expect it - emotional drama.

Steeltown Murders tells the real life story of a series of rapes and murders in and around Port Talbot near Swansea in 1973 and the reopening of the case in 2002 when new DNA evidence was unearthed. The rape and murder of sixteen year old Sandra Newton and the double rape and murder, two months later of Geraldine Hughes (Calista Davies) and Pauline Floyd (Jade Croot) after leaving the Top Rank nightclub in Swansea. Geraldine and Pauline were also both sixteen.

DSI Jackie Roberts (Karen Paullada) appoints DCI Paul Bethell (Philip Glenister/Scott Arthur - many of the characters are played by two different actors in each timeline and in such cases I've named the 2002 actor first and the 1973 one second) to lead the investigation and Bethell, who'd hoped to head up a much bigger team, calls up his old colleague DC Phil 'Bach' Rees (Steffan Rhodri (Dave Coaches from Gavin & Stacey)/Sion Alun Davies) and DC Geraint Bale (Gareth John Bale), a man too young to have been involved first time around.

Bethell, himself, has some demons and regrets regarding the case and is clearly seeking his own personal redemption (in this, Glenister reminds me of his older brother Robert in last year's Sherwood) as well as justice. Back in 1973, Bethell had believed that Sandra's murder at the hands of man who was dubbed the 'Saturday Night Strangler', should have been linked to those of Geraldine and Pauline but he was overruled on that by his authoritative, unlistening, and borderline bully of a boss DCS Ray Allen (Oliver Ryan) and the boozy joker DI Tony Warren (Steve Nicolson).

Time proved Bethell right about the case but, elsewhere, his tunnel vision leads him into trouble and, ultimately, the murderer was never brought to justice. Many of the cops suspected Sandra's married on-off boyfriend John Dilwyn Morgan (Rhodri Miles/Ben McGregor) but others, Bethell included, felt that Sandra's stepfather Dai Williams (Keith Allen/Rhys Rusbatch), a taxi driver, was the most likely culprit. Both men, in their small community, ended up being tried in the court of public opinion and suffered years of misery for a crime they had not committed.

The focus, initially, was on Geraldine and Pauline and less on Sandra. Because Sandra was sexually active the police took rape off the table which is shocking even for the police. Even in the 1970s. When the cases are, nearly thirty years later, finally officially linked it becomes clear that the hunt now is for a serial killer.

Under the shadow of the huge industrial steelworks complex, the hunt takes in the targeted swabbing of hundreds of men, press interference, double allels (I had to look that up on Wikipedia and so can you), a Dutch psyhic (Mr Croiset, played by Walter van Dyk) in a bowtie, budget cuts and lack of police resources, exhumation of dead bodies, and the danger of dredging up terrible memories for lots of people as well as the danger of repeating the same mistakes made first time around. Or even making some new mistakes. It will involve, as more than one character says, "a lot of shoe leather".

The police of the 1970s are shown to be heavy handed and to, far too often, act on personal biases and suspicions. Often they seem more interested in drinking and smoking than doing their job but, hey, it was a different time. As the soundtrack of Status Quo, Mott The Hoople, and Free makes abundantly clear.

Priyanga Burford is superb as Geradline and Pauline's friend Sita Anwar (played as a teenage girl by Natasha Vasandani - also very good). Now a headmaster, Sita is crucial to both the development of the plot and features in many of the most moving scenes in Steeltown Murders. Like Bethell, she has carried unnecessary guilt with her for decades and is looking for something like closure with the reopening of the investigation.

Both Paul Bethell's and Sita Anwar's personal storyline arcs, much of Bethell's comes out in expositional scenes with his wife Karina (Nia Roberts/Elinor Crawley), make for good, great even, drama but I did wonder about the veracity of them. There does seem to be an element of speculation at play here.

But if that's what's needed to tell this story so be it. It didn't seem exploitative and added another layer of humanity to a story that was already full of emotion. With a suitably ominous score courtesy of Sarah Warne and noteworthy performances by Richard Harrington as forensic scientist Dr Colin Dark, Sharon Morgan as Dai's wife Pat, William Thomas (and Grufudd Glyn) as Geraldine's father Denver, and Aneurin Barnard and Nicholas McGaughey as suspects Joseph Kappen and Thomas Willoughby, Steeltown Murders is a well put together ensemble piece that takes an episode to get into but then flies by.

There's not a lot of humour (though there is a very dark scene about how a rapist smelt so strongly of tobacco that his victim's mother stopped smoking - so at least some good came out of it) and nor should there be with this kind of subject matter. There are a lot of scenes where people who'd received the worst news imaginable back in 1973 are now faced with the prospect of receiving yet more bad news. Or, maybe, some news that's almost good. You'll be desperate for Bethell and Rees to solve the case and see justice done and even if you know how this story panned out in real life you'll still want to watch Steeltown Murders right to the end. Though you probably won't find yourself hankering after the 1970s much.