After blowing the whistle on a colleague Detective Grace Narayan is sent to a small Welsh island; there she encounters local GP Doctor Pridaux who explains that his son Cai vanished a year ago, but the investigation proved fruitless.
An identification is made of the body and Grace is keen to prove it was murder, but a murder investigation team arrive from the mainland and take over proceedings.
A huge storm hits the island, forcing Grace to spend time with all the locals under the same roof; Grace continues to investigate Cai's death; Silas provides an interesting lead, The True Way.
Grace is adamant that Gruffudd is somehow involved in Cai's death, and she tries to get to him, through Minh; Doctor Pridaux provides Grace with a credible lead after spotting a detail in the photograph.
Grace learns exactly what's happening on the island and all the questions that she had about The True Way are answered; the murderer is brought to justice.
Police sergeant Grace Narayan uncovers a cold case, pagan worship, and a community bound by eerie rituals on a remote island.