You went to a party the Arctic Monkeys organized to celebrate the new release of the AM album that Alex, who knows why, didn't want you to listen to it. It was funny how they organized it because they agreed to sing all the songs on the album, it was basically a little private concert.

they sang all the songs, and the last one they sang was "R U Mine?". Alex kept staring at you as he sang throughout the song

As they finish he comes to you

"So babe? are you mine?"