Sat on the top of a bus a couple of weeks before Christmas, Emma sees a couple arguing violently in the middle of a crowded Regent Street. They see her watching, she looks away, and the woman disappears. Emma goes to the police, who shrug and send her away. Then a body turns up... Now convinced she is a vital witness to a crime Emma is sent into hiding in rural Wales. She resolves to get to the bottom of the mystery, but then the snow comes and no one can get out. But what if someone can still get in?