'You knew right at the beginning. She knew he was never going to stop looking at other women. She knew he couldn't save money. She knew he was contemptuous of her...But then she somehow let herself un-know what she knew.' Grace Sachs, a happily married therapist with a young son, thinks she knows everything about women, men and marriage. She is about to publish a book called You Should Have Known, based on her pet theory: women don't value their intuition about what men are really like, leading to serious trouble later on. But how well does Grace know her own husband? She is about to find out, and in the place of what she thought she knew, there will be a violent death, a missing husband, and a chain of terrible revelations. Left behind in the wake of a very public disaster, and horrified by the ways in which she has failed to heed her own advice, Grace must dismantle one life and create another for herself and her child.