Adrian Monk: I didn't see that last week. Must've been covered up.
Natalie: What?
Adrian Monk: From here to here, it's been vacuumed. She vacuumed part of the rug.
Natalie: Well, what does that mean?
Adrian Monk: It means she didn't walk in on the killer. He walked in on her. He knew she was here. He must have heard the vacuum. He was after her. This was all about her.