Apathy
The police find signs of blood having been cleaned up from Nick and Amy's home. When they question, Nick he is apathetic towards his wife's disappearance. His apathy is a symbol of guilt to those investigating him and begins to make him the prime suspect in Amy's murder.
Diary
Amy has kept a diary of her time with Nick as she's become more and more isolated from life and from him. This diary becomes a symbol that the police's suspicions are looking correct that Nick is to blame, and also that Amy has created an elaborate plan to destroy Nick for what he's done.
Framed
Amy steals urine from her pregnant neighbor for a pregnancy test, drains her own blood to put in the home and then cleans it, and write a fake journal about Nick. All of these become symbols of her deep hatred of Nick and her desire to frame him for her murder.
Performance
Nick goes on a talk show in order to proclaim his innocence and to ask for Amy to come home. This is a symbol that Nick too is playing the game with Amy just as she has by creating the allusion that Nick murdered her.
Expecting
Nick and Amy announce on television that they are expecting a baby. This is a symbol of how the media can portray to the world a particular mood, such as happiness, when in reality it is all formed through lies and deceit from two people that want nothing to do with one another.
