Slipping the cap back on the vial, Sebastian returns it back to its place in the box and shuts the lid, relocking it before he addresses Steph, "You're not wrong. Thank you for bringing this and taking such good care of it."

He's a bit cool, but it's nothing to do with here so much as it's the sudden glut of Dumbledore's private pensieve and memories. What is he to do with all this information? When he knows that no moral argument will stave off his curiosity, should he even worry about what he now owns?