An irresistible bribe brings ten people together on a remote Hebrides island. They are here to take part in a psychological experiment on fear conducted by the unknown Dr. Crogil. But marooned by an increasingly violent storm, they soon realise the doctor's intentions are far more sinister... As guests begin to fall, one by one, it becomes apparent that this is a plot to murder them all. With each death, a single line of the traditional Magpie Rhyme is unpicked from the prominent verse displayed above the fireplace. Cracking under the pressure, the guests begin to believe they have no option but to accept their fate. Trapped, the tension rises. Who is Dr. Crogil and where is he hiding? And will he reach the tenth magpie before they find him? One for sorrow, two for joy...