The startled change in Jack's face isn't one of fear. Concern, confusion, but a desire to understand, underneath it all. D is trying to tell Jack he's a danger, warn him away. But whenever the conflict of 'safety' versus 'gaining new information' comes up in Jack's life, he always falls on the side of satisfying his curiosity.

"Monster? Again. Relative term. Open to debate."

Jack needs to have more care about how he words his question than he usually does with his words.

"Why do you fear what you'll do without a restraint?"