At her question, Derek looks a little thrown off. He's new to all of this. He might be Perimeter Guard but that doesn't mean he knows the ins and outs of everything. He neither knows whether it's all right for her to suggest a split to the others nor whether it's all right for him to split away from the group to go with her. One of them has to give. It's easier to feign ignorance if he's going his own way, because he can just say he thought she was Perimeter Guard and didn't bother asking to confirm.

Derek's that kind of guy: it's a lot easier for him to throw himself under the bus than someone else, even if he really ought to do it the other way around sometimes.

"No idea. All right, let's just...we'll go check it out and take it from there, how's that?" he asks, figured maybe that strikes a compromise they can both live with.