The build-up to George staking Mitchell. First Mitchell's attempts to convince George to do it by telling him that their entire friendship was a sham, and that George is pathetic. The fact that George knows he's lying is a Tear Jerker by itself. Then, when Mitchell doesn't have the heart to keep that up, he breaks down and begs George to do it because he knows he'll kill again. Finally George agrees. Mitchell says he's finally doing the decent thing, and Nina says this is what they'll remember him by. He tells Annie that she's the love his life. When Wyndham interrupts them, we think that this is a reprise (albeit not a particularly good one). Wyndham informs Mitchell he'll have to be an "attack dog" for the Old Ones, or else he'll "crucify" George and Nina. George picks up the stake, apparently to kill Wyndham, then turns around and rams it into Mitchell's heart.
George: I'm doing this because I love you.
Mitchell: I know.