 CONT: When Laurie jabs the needle in Michaels neck, he sticks the  butcher knife in the couch. After Michael falls, Laurie picks the  knife up, looks at it, and then throws it on the floor next to the  couch. Later, Michael comes upstairs holding the knife. Before the  end credits, when we hear Michael breathing and it shows all the  shots of the house, the knife is still on the floor next to the  couch.