Natty and Sean Wainwright are happily married. Rock solid in fact. So when Natty's oldest friend, Eve Dalladay, appears - just as their daughter collapses on a school trip in France - Natty has no qualms about leaving Eve with Sean to help out at home.
Two weeks later and Natty finds Eve has slotted into family life too well - her husband has fallen in love with Eve. He's sorry, he tells her, but their marriage is over. With no option but to put a brave face on things for the sake of the children, Natty embarks on building a new life for herself. And then she receives the note. Eve has done this before, more than once, and with fatal consequences...