Police sergeant Grace Narayan is sent on a 'punishment posting' to the small, antiquated island of St. Jory, where she discovers the forgotten cold case of missing teenage boy Cai.

After the body is discovered, Grace is convinced something sinister is at play, but mainland police disagree. She investigates to see if Cai's death was accidental or if there is a murderer loose on St. Jory.

The Widow's Wail, a mighty annual storm, brings the islanders to the village hall for fun and refuge. Trapped inside, Grace is on edge, wondering if Cai's murderer is among them.

The word is out that the True Way were involved in Cai's death. As the island reels, an obvious suspect emerges, but Grace's theories could about to be turned on their head.

After ruling out the True Way, Grace turns her suspicions to Gruffudd. But the island seems to be galvanising for something else.

With Cai's killer caught, the True Way takes control of St. Jory, threatening their own form of violent justice. Grace tries to restore order, but faces chaos.