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.

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.