[ they don't need to say "I don't know" for him to read it in their half-an-expression and their uncertain tone - and it stings, just a little, but Lupin is patient and understanding and knows that however confused he feels now, they have it a hundred times worse. So he waits for them to organize their thoughts, unwilling to give up. And when the unspoken answer in the words that fall from their lips leans towards the positive, he exhales quietly, thankful that the worst didn't come to pass (even if he didn't think it would.) That's enough for him to believe. More than enough.

How can he trust them? How could he stop now, after everything they've been through? ]

I've met Ghost. They wouldn't do or say half the things you have to me. This might embarrass you, but I've gotten pretty good at telling when you're not being honest.

[ if the feelings in their voice when they said his name while they were alone together haven't been the real deal, he'll eat his hat - and they might have a sterling career as a master thief and trickster in their future, themself. He draws his fingers affectionately along their cheek, paying no mind to the cracks and splits, until his thumb grazes the edge of their lips. ]

Besides, I do love you. If I didn't trust you, I wouldn't be much of a partner at all. [ Cairngorm might not be able to see it, but Lupin smiles anyway. ] What I said back when they vanished still stands. When it comes to the two of you... Maybe a human like me will never completely understand, but I'll still be here to figure it out with you.