Trecho da sinopse da Wikipedia, que você realmente vinculou a si mesmo:
Presumivelmente, Arthur estava esperando em (ou perto) da casa e emboscou-a quando ela voltou.Right before he is killed with a framing hammer, Arthur tells Dexter "It's already over." Disposing of Arthur's body on his boat afterwards, Dexter comes to realize that his love for his family is starting to outweigh his need to kill, and he begins to hope for a future without killing. But upon returning home, he finds a message from Rita that she came home from the airport because she forgot her identification. Dexter returns her phone call, only to find that Rita's cell phone and bags are in the house.