Students Hayley and James are young and in love. After saying goodbye for Christmas at a London train station, they both make the same mad split-second decision to swap trains and surprise each other. Passing each other in the station, they are completely unaware that they have just swapped Christmases.
A young couple arrive at a retreat in the English countryside in the hope of saving their failing marriage. But when the people around them start to be picked off by a vicious killer, the weekend becomes a matter of saving their lives.