New Year's Day, Inverness airport and a seasonal burst of highland snow grounds all flights. Lucy Blue finds herself agreeing to share her hire car and the drive back to London with a total stranger.

Their drive becomes a journey through a winter wonderland, a cocooned world inside a world. For just a few hours Lucy is separated from reality and finds herself thinking and behaving in a way she never would in normal life.

And then several weeks later, when life has almost re-established itself and Lucy tries to forget, an ad appears at her local tube station, a small red car at the top, and in bold lettering: Lucy Blue, where are you? . . .