Castiel noticed Anna leave, knew she had planned something with Aziraphale. She had gone to get someone, she was coming back.
It was a foolish thing to do and all the time she was gone he became more agitated. Why wouldn't she listen? Why did she have to be so stubborn? She had always been like that and it made no sense at all. Did she want to be captured.
"You need to go, you need to go and take Anna with you," Castiel said to Aziraphale. His voice was detached as he sat on the floor. He started rocking back and forth slowly, clawing at his own back with long, deliberate, strokes like he was shredding newspaper.