Read some of Tory's posts on the dirty tricks she has received. A big part of it is "messing with your mind". Like you come home after work and find a can of baked beans in the middle of your kitchen table that you didn't put there, and the door is still locked etc. with nothing taken or damaged. In other words, they just wanted to show that they could enter your house any time they wanted to.
(The can of baked beans is my off-the-cuff example, not something Tory wrote. I don't recall the specifics she gave.)
Ok, now I understand. Thanks, Paul and Tansy. Yeah, that would mess with your head!