What CSI Episode is this?

Okay, so my friend was talking about this one episode where A guy lives in someones attic and drills a peep hole through ceiling. When they leave he goes under there beds and waits for them to come back. then he kills them and mutilates their body parts. He also walks like a spider and a black suit. I want to see this episode, I just don't know what it's called! What is it called? xD