If what Jack's doing is a smile then Carpenter's The Thing is a friendly household pet.

"Only one person w-who's still alive."

For the record, he hasn't backed off a single step. It's not that he knows of a reason to mistrust Sinclair specifically. But there's nothing like a room full of souvenirs of your last major hoodwinking to put the scare in you.

"And it doesn't work any more."