The story of the acid murderer's first victim is revealed, as another suspect enters the frame. Gabriel receives some help in his investigation from an unexpected source - but is the situation more complex than it seems? As Gabriel indulges in reckle... (more)ss, self-destructive behaviour that could jeopardise everything, he is blind to the possible consequences of the life that he is leading. The casual cruelty of Gabriel's vanity is exposed, and his relationships come under more strain. Meanwhile, the team have to face up to the fact that they have a serial killer on the loose and begin the hunt in earnest. As Gabriel sets his sights on tracking down the first suspect, Elaine makes a difficult decision to revisit her past. Finally, while tracing the journey of the first victim's final steps, the identity of the killer is unmasked.