Julie doesn't come home one night; the next day as she is getting out of the pool we see that she has been "roughed up" and has a black eye. Next to her eye there is a circular bruise/mark. That evening, as Julie and Sarah are at dinner the bruise is now under Julie's eye and is a different shape (longer and more oval in shape).
Near the end, the publisher tells Sarah Morton that he is disappointed in her latest book and asks her "Where's the plot twist?" Interestingly enough, the viewer is presented with a very big plot twist a short while later as the movie ends.