On an altar lies the body of a local teenage girl, the precociously talented Katy Devlin. Her body is found in the middle of an archaeological site, threatened by local developers aiming to build a shiny new motorway.

Despite Rob's promise to Cassie that they won't investigate Operation Vestal because of Rob's intense relationship with Knocknaree, he convinces her that they are the best people to solve this case.

All of Knocknaree mourns as Katy Devlin is laid to rest, while pressures on Rob and Cassie mount as there are still no arrests in the case.

Cassie struggles to make sense of Lexie's life and death, while Rob's past finally yields some results in the Katy investigation.

Cassie prepares herself for an undercover assignment. Elsewhere, Rob hits rock bottom. Could a past memory be the key to everything?

While undercover Cassie feels herself being seduced by Lexie's world and friends, Rob desperately hunts down one more lead.