The Harrison family gathers as usual for Christmas in their big Sussex house. This year, however, outside realities are pressing hard: Pamela and John, married for four decades, know that time is catching up with them. And trouble is brewing in the lives of their four children. Cassie, the cossetted youngest, is in the throes of an affair with a married man; Elizabeth, her awkward older sister, is struggling with a faltering second marriage; Peter, the eldest and designated inheritor of Ashley House, is beginning to meet resistance to such a prospect from his career-orientated wife. Only Charlie, the charming and carefree younger son, and his wife Serena, seem truly content, with nothing to worry about except their adolescent twin girls and the simpler teething troubles of their toddler. Absorbed in their own lives, not one of them is prepared when real tragedy strikes, rocking their world to its core, changing them all forever.