Stupidity: At the end of the movie when Laura discovers that all the cans are neat in her cabinet, she knows she has to leave the house. There's a back door to her house, but she runs up the hallway to the front of the house. She could've been out of the house in seconds going out of the back door, but of course that would've ruined the end of the movie.
Stupidity: When Laura goes back to the house to get her bag, she takes off her wedding ring and flushes it. Problem is, she knows how her husband is and doesn't take the time to make sure the ring goes down! But she makes sure there's no other trace of her being there (flushing her hair down the toilet and drying the floor off from her wet feet!).