Just when it seems like Catherine is gaining control over her life, she discovers that Tommy, whom she holds responsible for her daughter's suicide, has been released from prison after serving time for other offences.

Catherine becomes consumed by the idea of confronting him, unaware that Tommy is involved in a criminal organisation with the intention of kidnapping Anne Gallagher, the daughter of a wealthy businessman, for ransom.

18 months after the first series, Catherine is back at work and has been awarded the Queen's Police Medal (QPM) for gallantry, for rescuing Gallagher from Royce, who is serving a life sentence in prison.

Gradually, their investigation leads them toward Victoria's actual killer: police detective John Wadsworth, whom Fleming had been blackmailing.

Catherine's grandson, Ryan, develops a friendship with a new teaching assistant, Miss Wealand, secretly a prison groupie infatuated with Royce.

Taking place seven years after the events of the second series, Catherine is coming close to retirement age and has plans to go on a hiking expedition to the Himalayas.

She is called to investigate the discovery of human remains found near a reservoir, where she comes to realise the murder suspects share a history with Royce, who has since been transferred to a jail in Sheffield and is awaiting trial for a string of unspecified offences.

Ryan is also having problems at school with his PE teacher, Rob Hepworth, who has kicked him off the football team following accusations of misconduct.

The main character, Sergeant Cawood, is mentioned in the third episode of the fifth series of Last Tango in Halifax, which aired on BBC One on 9 March 2020.

[13] Radio Times called Happy Valley a "word-of-mouth hit" which "steadily became a success outside the normal audience for the slot and channel.

However, some reviewers have criticised the show for its graphic content, especially in episodes three and four of season one, while others have noted the ubiquitous typecasting of male characters as either weak or criminals.

[17] In response to the criticism, Happy Valley's creator-writer, Wainwright, defended the show as "a quality, well-written drama" and stated, "Judging by the amount of email, texts, tweets I've had, I don't think anyone is asking me to apologise.

"[18] In an interview with the Radio Times, Wainwright said the level of violence had been carefully considered, and it was done responsibly, by showing the psychological and physical damage suffered by Catherine.

"[20] Gerard O'Donovan of The Telegraph called Happy Valley "complex, thrilling and brilliantly written and acted", and "one of the best watches of 2014".