The flat was clear, so Rook decided to lie in wait for his only friend. Which might have seemed like a strange thing to do--hide in your friend's home until they get back so you can attack them--but Rook had never really been one for doing things 'normally'. Clearly. While he waited, he looked around and went through some of Dax's things, partly out of boredom, and partly because he was just nosy. He put things back where he found them, but didn't take special care to make sure the other man wouldn't know he'd been there. That wasn't the point of this exercise. If it had, he would have left by the time Dax got back.
He was in the bedroom when he heard the front door, and put down the last thing he'd held in his hands. Dax seemed to be slow coming into the flat, so Rook waited a moment to let the silence stretch between them, seeing if it would lull the other man into a false sense of security, then fired a disarming charm at him as a warning as he threw himself out of the bedroom.