A disturbance at the office brings Diarmuid and Rob out in force only to find that the office has been ransacked and a young man lies gravely ill on the ground. An even worse sight awaits Diarmuid on the roof - the sight of his teenage daughter falling over the edge. While Erin fights for her life in hospital, while the young man loses the battle for his, it is revealed that a so-called 'legal-high' is to blame.