The team investigate the discovery of the decomposed body of Naomi Bancroft nearly two years after her disappearance. Allie takes a personal interest in the case as her former mentor was the lead investigator on the case at the time of Naomi's disappearance. But the new investigation takes a number of twists and turns before it turns up a stalker of Naomi's who may hold a key to her killer. Meanwhile, Matt becomes frustrated at being asked by Emma to give up his job and move to France with her.

The team go on the trail of a vengeful father who has gone vigilante on thugs who got off with light sentences after the murder of his son. It comes to a stand-off between him, his son's killer and Detective Buchanan. Meanwhile, Emma and Matt split up after she decides to take a new promotion in France.