"But we didn't find her, it let her go. Why?" Again it was a question that he didn't think Susan was going to have an answer for. Hank was just asking the questions out loud that he had been asking himself over and over again in his head.
He was getting ready to stop pacing again, when Susan said what she said about Janet needing him. He almost laughed, he didn't think that Janet wanted him around right at the moment. He didn't blame her, he wasn't enjoying his own company at the moment.
Still while Susan was a friend he wasn't going to say that to her. Instead he picked up the tests and put them back down. "I'll have to let her know everything came back clean. Completely clean." He thought that Janet would feel the same way he did - not relieved.