She stayed in your house. Now she wants your life . . .

We all have that friend - the one who doesn't quite belong. Dinah Marshall is that person and knows it. After someone drops out, she's invited to spend the weekend at a luxury holiday home with women she's known since university. However, the gulf between them has widened since then, and Dinah is conscious of being the only one with no money, career, partner or children. Feeling like an outsider, she takes to snooping around the house. She's fascinated by its owners, Sarah and Isaac Rivers - and when she discovers she can secretly stay an extra night, that fascination quickly spirals into obsession.

When Isaac Rivers meets 'Diana Malone' at an exclusive members club, he introduces her to his wife and friends, and she's soon welcomed into the group. She seems to be trying a little too hard, however, and as her somewhat intense behaviour starts to raise both eyebrows and questions, one of her new acquaintances begins to suspect she isn't who she says she is. For Diana - or is it Dinah? -this is a disaster: she's worked hard to get where she has, and these suspicions threaten everything. But Diana isn't the only one with secrets, and if she's going down, then she might just take everyone else with her . . .