PUPPET ON A STRING (HAPPY VALLEY, SERIES TWO)

Rules are always there to be broken for any accomplished screenwriter.

And that's the way it is with the second series of 'Happy Valley'.

Fans of the show will know from the first series that Sarah Lancashire's character Sergeant Catherine Cawood has a nemesis - James Norton's violent sex offender Tommy Lee Royce.

He's the man who fathered her grandson, Rhys Connah's Ryan, although he denies it was through rape.

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Ryan's mum subsequently committed suicide, with Catherine's decision to raise the boy destroying her marriage to Derek Riddell's local journalist Richard.

(SPOILER ALERT)

During the first series, Tommy murdered a police colleague and a co-conspirator during the abduction of Charlie Murphy's Ann Gallagher.

He also raped her.

However he ended up behind bars after Catherine tracked him down with the help of her sister Siobhan Finneran's Clare on a barge he was hiding in.

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But this was after Tommy had made contact with Ryan and had doused the boy in petrol.

With Tommy in jail, director Sally Wainwright doesn't take the easy option in the follow-up series, finding a way to weave him into the story without getting him back on the streets.

She figures out a way to continue the feud with Catherine while Tommy languishes in jail.

And she does it brilliantly.

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Series Two begins with Catherine investigating a case of sheep rustling.

This ends up in her discovering rotting human remains in a garage.

The corpse turns out to be Lynn Dewhurst, Tommy's mum.

Catherine, however, faces questioning from a team of detectives investigating the case, Vincent Franklin's DSU Andy Shepherd and Katherine Kelly's DI Jodie Shackleton because she left angry messages on the victim's phone.

But when other bodies start to pop up, speculation mounts that a serial killer is at loose in the neighbourhood.

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This being 'Happy Valley,' though, the second series isn't just about this crime.

Catherine has a new trainee under her wing, Ann Gallagher.

Eager to carve out a new career after her ordeal at the hands of Tommy, Ann has to deal with the passing of her mum Helen from cancer - a good friend of Catherine's sister Clare.

That means helping her millionaire businessman father, George Costigan's Nevison handle his grief.

Clare, meanwhile, runs into Con O'Neill's Neil Ackroyd, an old school friend who has had a messy divorce and, like her, has battled addiction.

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Romance blossoms but Neil is also a bit scared of Catherine because of a past encounter with her in her capacity as a police officer.

Catherine, however, is more preoccupied with helping protect a Ukrainian woman, Ivana Basic's Ilinka Blazvic who she rescued with 20 other women trafficked illegally into Yorkshire by a local crime gang, the Knezivics.

Karl Davies' Daniel Cawood, Catherine's older son, is also back living at home following the break up of his marriage.

This allows him, though, to bond with Ryan.

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Catherine is approached in the line of duty by Susan Lynch's farmer Alison Garrs after her loner son, Robert Emms' Daryl is repeatedly harassed by youths in their town.

Angered by the treatment of the Garrs, Catherine leans on the blokes responsible but they still harass Daryl.

Meanwhile one of the detectives investigating the recent spate of murders Kevin Doyle's John Wadsworth, who is married to Julie Hesmondhaglh's Amanda, is having an extramarital affair with Amelia Bullmore's Vicky Fleming.

Hoping to meet her and break it off, he suddenly finds himself under the cosh with Vicky blackmailing him into leaving his wife and kids.

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If this wasn't enough, Tommy is still trying to make contact with Ryan from jail.

He does this by manipulating an infatuated girlfriend on the outside, Shirley Henderson's Frances Drummond into heading to Calder Valley to land a job as a teaching assistant in the boy's school.

How will Catherine deal with Tommy's attempts to bond with Ryan?

And who is the serial killer violating the corpses of local women?

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Once again, Wainwright and her fellow director Neasa Hardiman do a superb job crafting six taut episodes in the second series of this compelling drama.

No misstep is made as they spin several storylines and coax wonderfully grounded performances out of their cast.

Lancashire's Catherine Cawood remains the beating heart of the show, stoically shouldering the twin burdens of policing a fractured local community and managing her own dysfunctional family.

It's another wonderfully modulated performance from a lead actress who knows exactly when to seize her dramatic moments and also when to let others shine.

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Norton is equally deft, shifting at the appropriate moments from Tommy's cold, calculated manipulation to raw, feral anger.

As with the first series, it has to be said the performances are uniformly strong throughout the cast.

Finneran is as compelling as ever as Clare, giving the audience their first glimpse of her vulnerability as she briefly falls off the wagon.

Murphy is terrific too as the reconstructed Ann but underneath the surface of her enthusiasm for her new role in the police, there are hints of the trauma of her experience at the hands of Tommy.

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Costigan exudes old fashioned decency as Nevinson as he tries to be the compassionate husband his late wife wanted him to be while admitting his own failings.

Henderson is excellent too as the easily manipulated Frances, while Doyle is wonderfully twitchy as his character flails about under the pressure of a disastrous relationship with Bullmore's other woman.

Matthew Lewis brings a vulnerability to the role of an ex-offender Sean Bamforth who has been given a chance by Nevison to build a life out of prison but who becomes a person of interest during the police investigation into the murders.

Kelly and Franklin are note perfect as Doyle's arrogant colleagues, while Rick Warden, Ishia Bennison, Shane Zaza and Mete Dursen are good value as Catherine's fellow officers on the ground.  

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Emms does his trademark introvert role which has become a really polished act, gelling perfectly with Lynch who again demonstrates why she is one of the most consistently strong supporting actresses working in British television today.

O'Neill does a decent job too, hinting at the deep damage inflicted in the past on Neil, while Hesmondhaglh, Davies and Basic strike the right tone in their minor roles.

Finally, Connah again impresses as a boy struggling to understand why his grandmother insists he can't have any contact with his dad in jail - especially when Tommy seems to be making all the right noises about wanting a relationship with him.

With its perfectly pitched shifts in tone and its lean dialogue, aspiring screenwriters would do well to study Wainwright's scripts for both series of 'Happy Valley'.

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There is no dialogue wasted, nor does she revert to any incredulous plot developments.

Wainwright knows exactly when it is appropriate to raise a laugh and when to make events appear to spiral out of control.

Although she never loses her grip.

When there are big set action pieces in the show, they always feel in the service of the show and not like a desperate attention grab.

Wainwright doesn't put a foot wrong as she subtly opens doors to other storylines - like the Knezivic crime gang - that you know will eventually resurface.

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It takes a terrific writer to produce two gripping series of a show like this.

You only have to look at how Wainwright balances each storyline to realise how skilful a writer she really is.

So take a bow.

'Happy Valley' really is up there with the best of Jimmy McGovern's 'Cracker' and Lynda LaPlante's 'Prime Suspect'.

And what's really exciting is you can't help feeling the best has yet to come.

(Series two of 'Happy Valley' was broadcast on BBC1 from February 9-March 15, 2016)