Piper hadn't been kidding about making finding Daniel's blackmailer his main priority. He'd spent the night going over the known residents of the building, and even thought he didn't really think Shane capable, even he had to admit that it might be the best fit.
He knew Shane had killed someone, knew Shane sprouted claws and teeth and tried to kill him. Maybe he'd killed the guy in the alleyway, and maybe he thought Daniel had gotten wise. Maybe keeping Daniel locked up was the best way to ensure his own safety.
Piper couldn't discount him.
He'd never embarked on a spying mission before, but he knew how to be completely silent. It was something he'd played at as a child - trying to make no sound whatsoever, to experience life as his parents did.
Following Shane out of the building unnoticed was easy, but keeping track of him wasn't. A few alleys and sharp turns, and he'd lost him. That wasn't enough to make Piper give up, however. He wandered, and he listened, his hands shoved deep in his pockets, his thoughts completely focused on listening for any signs of Shane.