Truthfully, the last thing Castiel had time for was to be chasing after demons, but in her hands, that weapon could cause more damage than even she was aware of. He needed it back, if only to keep a certain amount of order.
He was also well aware of how he felt when Meg was around. It was...unlike anything else he'd ever experienced and he didn't want to label it as simple lust because angels did not lust. Even though he had and he knew it.
Honesty was in short supply these days.
"Return the weapon," he said firmly. "And if you tell me what you know of your arrival here, I will allow you to get away unscathed."