"Hey?" Stiles repeats. He's staring. He knows he's staring. Derek is not a sociopathic vampire intent on killing him for getting his wife fired, so he needs a moment to be incredibly relieved before he begins to tackle what the hell Derek is doing there.
He narrows his eyes, squinting in the darkening twilight. "What are you doing here? Have you been following me? Is this a thing you do now? Lurk menacingly in your car? I can't believe you have the same car, by the way," he adds, incredulously.