Janie has been avoiding John ever since Clarke learned the truth about their partnership and put her promotion on ice. But an unexpected gesture from Clarke's boss sees John's role as a consultant with Mid Wales police made official. This forces John and Janie to find a new normal and rekindle their connection. They're tasked with solving the murder of Janie's mechanic, Dean Ward, which took place during a school reunion party at Janie's old school. As John and Janie dig deeper into Dean's death, links emerge to DC Chaudhry's recently unearthed cold case, a body uncovered in a drain. This forces Janie to revisit the events that led to her teenage best friend Sian's suicide fifteen years ago. John's instincts about the case puts him and Janie at odds, eventually forcing them to acknowledge the importance of their friendship. But as the series comes to an end, John upends their reconciliation with unexpected news…

A murder mystery event turns into a real murder investigation when famous Welsh actor and TV detective Anthony Hart is found stabbed to death at the dinner table. There's a lot of pressure on Janie to solve this murder, which isn't helped by the fact that John is close friends with Helena Hart, the sister of the deceased. John and Janie's investigation reveals not only a feud between siblings warring over property and their family's legacy, but also the pitfalls of fame and the kind of person Anthony really was. John finds himself rekindling his fledgling romance with old flame Helena, but ultimately, it's through an unexpected connection with a suspect that he is reminded of the dangers of living in the past, which inadvertently helps Janie let go of her own baggage. For Janie, this case is also the final hurdle before landing her DI position.

Following the murder of coastal town businesswoman and am-dram theatre director Menna Hughes, Janie is eager to solve the case and land the DI promotion she desperately wants. She enlists John's help, but bristling at Janie's insinuation that he might have ‘lost' his acting chops, John takes matters into his own hands and joins the cast of the theatre group's next play. What starts out as a murder investigation soon becomes a cathartic journey for John, who is unexpectedly reminded of why he fell in love with acting in the first place. As for Janie, witnessing a downtrodden suspect finally stand up for themselves inspires her to confront her own demons from the past.

Janie is tasked with solving the murder of divisive best man Gethin Bennion the night before a wedding. What initially seems to be a burglary gone wrong quickly unravels complicated family dynamics and betrayed friendships, revealing just how far people will go for love. Janie is forced to face up to her personal experience of a friendship turned sour in order to connect with a suspect and crack the case. Meanwhile, John forms an unlikely connection with one of the suspects over art and painting, forcing him to re-evaluate the role that work played in his own marriage and the circumstances around his late wife's passing.

After a walker is found dead on a Welsh mountain trail, John's insight into the unidentified woman quickly turns this into a murder investigation. Janie ropes John into joining her mam Yvonne's walking group to help solve the case and crack the identity of this mysterious woman. John is reluctant to go out and socialise, but he can't resist the call of another mystery. John and Janie join forces to solve two mysteries: the identity of the victim and a cunning murder plot with a large dose of blackmail and revenge. Janie's fierce defence of one of the suspects reveals more about her past, while John finds himself out of the house and enjoying himself a lot more than he's ready to admit...

Disarming Welsh DS Janie Mallowan is desperate to solve some big cases and progress her career. While investigating the death by apparent suicide of wealthy property developer Carwyn Rees, she meets none other than John Chapel, the retired actor who played her TV detective idol, Inspector Charles Caesar. Eccentric and reclusive John uses his insight into character to deduce that Carwyn was murdered, though Janie is initially sceptical of his conclusions.

When forensics prove his theory right, Janie quietly asks him to help with the case. Having shut himself away from the world for years, John is initially reluctant to help. But together they work to solve an intriguing mystery involving an environmental activist, a grieving widow and a bitter business rival, painting the portrait of a man who kept a lot of secrets from those closest to him. And although John and Janie are not ready to admit it, this first case is the start of an iconic crime-solving partnership, and a friendship, too.