After using the same route to drive to the in-laws for 20 years, Frank decides to take a short cut. As he and his family drive along a forest-smothered road on Christmas Eve, he spots a lone woman at the roadside and stops to offer assistance. Naturally, the ghostly figure eventually disappears and, one by one, so do the family members - discovered later in a bloody heap.
With most of the story staged either within the moving vehicle or on the featureless road, it is the interaction between the characters that is the most interesting feature. As the situation becomes more harrowing and bizarre, the panicked characters confess intimate secrets, resulting in a decent dose of dark humour.
The movie defies logic, but raises the odd scare, generates many laughs and produces a sufficient feeling of puzzlement and apprehension throughout.