Katie Lavender has always thought she was pretty unshockable, until a year after her mother's death she receives a letter from a solicitor telling her that the man she thought was her father, in fact wasn't. Her real father, a man named Stirling Nightingale, has for years been building a trust fund for her. And now she's of an age to collect it. But Katie's not interested in the money. She wants to know about the man instead. So decides to do some snooping. She tracks him down to a beautiful riverside home in Surrey on the night he's hosting a birthday party for his 90-year-old mother. And as she's hovering outside, Katie is mistaken for a replacement waitress - an opportunity just too good to miss. And so Katie discovers that the Nightingales are far from your normal family ... But what makes a normal family anyway?