Thorne.... is not entirely surprised that Sento's hide-out is the basement lab from his dungeon. She's just glad it's nothing like Dr B's, despite them both being secret basement labs.

"Hokay. So," she says. "I've told Other Matthew where we are and I will still be walking you through actually doing this... but what you're basically going to do is to make just enough contact with his mind to distinguish between the two, find the one that's actually Stone... and pull it forward, into consciousness."