Detectives Rob Reilly and Cassie Maddox are on the case after 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 as there are still no arrests in the case.
Cassie prepares for the most challenging investigation of her lifetime; Rob hits rock bottom.
When Cassie embeds herself in Whitethorn House, threats both known and unexpected haunt her every living breath.
Everything comes to a head as Cassie confronts Lexie's killer and Rob has a breakthrough regarding Katy's murder.
Rob and Cassie are forced into a face-to-face reunion; Damien crumbles under questioning; as arrests are made, Rob and Cassie both come to profound realisations.