When a man is found tucked up in bed with his throat sliced open two days after Christmas, DS Jason Smith and his team are baffled. It appears he has been drugged, killed, and carefully wrapped up in a duvet. The only evidence Smith finds are some strands of hair belonging to a woman. One month later, another man is killed in exactly the same manner but there appears to be no link whatsoever to the two men apart from the fact that they were both single, lonely, and middle-aged.

In the midst of the worst winter in years, Smith and his team quickly run out of ideas and tensions between the detectives rise. Frustration leads to conflicts both at work and in their personal lives. The only clue the team has is the murders were carried out under the glow of the full moon.

Just when Smith feels like he has reached the end of his tether and his own sanity is declining, help comes from an unexpected source; a man who knew this woman when she was a young girl in the mountains of Northern Romania. He sheds light on the reasons these men had to die. Smith finds out who this woman used to be but who she is now is still a mystery.

Haunted by lucid dreams and terrifying double awakenings, Smith stumbles upon something that will send him on a hunt for the most baffling murderer the people of York has even seen. With time quickly running out before the next full moon and the safety of one of his closest colleagues entering the equation, Smith finally closes in on the most terrifying murderer he has ever come across.