Excitement reigns over the Thomas brothers' plan, but not everyone is keen on them. When an act of sabotage breaks the calm of the village, Prem finds himself facing his darkest hour.

It's now 1966, three years after Prem and Kamini's arrival, and they have become very much a part of the Trefelin community. But their lives and those of everyone in the village are about to change when its highflying 'prodigal sons' Basil and Robert Thomas, return to bring a first real taste of the swinging 60s. Prem, Emlyn and Owen are trapped underground - but no one on the surface knows they're in trouble. Basil's continuing drive to recruit buyers is reaping great rewards; most of the village have now signed up to the new town, while his brother Robert takes advantage of Emlyn's absence by attempting to seduce Megan. When it's revealed the mine collapse was no accident, revolutionaries Aled and Daf are prime suspects. Prem's investigations soon reveal Robert has a dark past whilst, with Dan's help, Kamini uncovers the real story behind the new town and Basil is forced to reveal his true ambitions.

Prem, Emlyn and Owen find themselves trapped underground following an unexplained accident at the mine. Basil continues to try and convince the villagers to exchange their deeds for new houses.

Prem and Emlyn find out that foul play is responsible for the collapse at the mine. Aled and Daf are the prime suspects, despite their protests of their innocence. Robert attempts to convince Megan to leave Trefelin with him, and it’s down to Prem to find out the real truth about his past.