When the team attend a Dark Morris Dancing event, the ‘Legend of the Knuckerhole Dragon', Margo finds herself at the centre of a crime when a member of her team collapses during their performance. With a severe allergic reaction to blame, and the victim's epi-pen case empty, Humphrey is stumped as to how the attack was triggered unseen whilst all eyes were on the stage.

As jealousy and secrets come to light, the targeting of the victim's allergic reaction begins to paint a sinister picture. And with a connection to the crime, Margo is put to the test as she goes undercover to see what clues a familiar face might hold.

Meanwhile, Humphrey and Martha take a big step on their homeowning journey, but Humphrey's mind is preoccupied when a powerful figure from the Hub arrives at the station looking for answers. Elsewhere, Esther is floored when Zoe suddenly reveals her decision to travel the world.

Humphrey and Esther are left baffled when a dogwalker leads them to a man painted green and bound with ivy. Delving into the mystery of the mythical Green Man, the team discover an off-grid community living off the land. But when their woodland home comes under threat from a developer from the city, tensions rise and accusations fly as the image of the Green Man continues to crop up at crime scenes, including painted across a developer's office as it goes up in flames.

Learning more from the two warring brothers who own the land, with one siding with the off-gridders, and the other keen to get the diggers in, it's up to the Shipton Abbott team to uncover the ties that bind and those that don't. But when one alibi doesn't check out, it seems the battle lines in this extreme sibling rivalry aren't as clear-cut as they seem, as dark secrets threaten to be unearthed.

Meanwhile, the pressure on Humphrey from Mr Smith continues to mount as the deadline to lose a team member rapidly approaches. A family dinner looks set to offer some respite, but things go from bad to worse when it turns out Anne has invited Mr Smith as her special guest. Elsewhere, a determined Martha shocks all around her when she takes on some of Margo's advice, leaving even Humphrey and Anne speechless. And Kelby is joined by Esther and Margo as he anxiously awaits Agnieszka's arrival from Poland. But as the night draws on and Kelby continues to wait, Margo's theory that he's being scammed looks all but confirmed...