A secret from his father propels Jack to Belfast. Meanwhile, Simone and Nikki investigate the mystery of a burned body. As familial secrets come to the surface, Jack faces tragedy head on.

Levelling-up leaders and environmental activists clash in a small town trying to look to the future. With a sabotaged train and a dead mayor, the activists become suspects.

The Lyell team return to the tunnel and uncover some difficult truths, while the police raid the protester camp, desperate for answers. Family ties are pushed to their limits.