When Olivia shows her notepad to Peter, there is something written in the left margin. In close-up, there is nothing in the left margin.
Olivia and Sam play the game of Clue. A standard game of Clue requires a minimum of three players.
When Walter is examining the victim who died after having lunch with the killer in the opening scene and he finds the hand print on her arm he says that it was the killer's right hand (he did touch her arm with his right hand). However the print on her arm was of a left hand. The angles of the hand indicate they were made by a left hand. Also the thumb print was on the inside of the victim's arm.