Double "date" HELP!

So my friend is helping me find a guy and she's trying to set me up with her soon to be boyfriend's friend. I don't know the guy very well, but he's really attractive! Anyway, all four of us are hanging out this Friday with a bonfire and then we're watching scary movies. I really want this to work out, but the guy doesn't know we're being set up. How can I get him to like me and want to keep talking after our "date?"