On the shores of a tranquil fjord in Northern Iceland, a man is brutally beaten to death on a bright summer's night. As the 24-hour light of the arctic summer is transformed into darkness by an ash cloud from a recent volcanic eruption, a young reporter leaves Reykajvik to investigate on her own, unaware that an innocent person's life hangs in the balance. Ari Thor Arason and his colleagues on the tiny police force in Siglufjoerdur struggle with an increasingly perplexing case, while their own serious personal problems push them to the limit.

As silent, unspoken horrors from the past threaten them all, and the darkness deepens, it's a race against time to find the killer before someone else dies...