[He doesn't catch on to the subtle difference in look and assumes it's because his student is there. It probably helps in Stein's favor that Kid doesn't seem to be doing well.]
What do you mean by that? Did something here mess with you? [He knows how that is, which can also work in Stein's favor]
no subject
What do you mean by that? Did something here mess with you? [He knows how that is, which can also work in Stein's favor]