A young girl is found murdered in the woods on the outskirts of Dublin, Ireland.

Rob and Cassie make a dark bargain to keep the secret and solve the cases.

All of Knocknaree mourns as Katy Devlin is laid to rest; the pressures on Rob and Cassie mount.

Cassie struggles to make sense of Lexie's life and death, as Rob's past yields results.

Cassie prepares for the most challenging investigation of her lifetime; Rob hits rock bottom.

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