Called to a domestic dispute, Eve is shocked to discover a woman tied to the bed, covered in make-up, wearing a stick-on tattoo and a partridge in a pear tree figure in her hair, strangled to death. Video footage reveals she had let a man dressed as Santa into her flat just before she died, and the hunt for the killer takes on a sinister new edge as Eve realises he is counting down the twelve days to Christmas.

As the murders continue, they discover that each of the victims have been chosen through the dating site Personally Yours. Eve enters the dark world where searching for The One is never satisfying enough.