Mary and John are at some secluded spot that looks like the same location used in Hookman. John's obviously ramping up to propose and Mary stops him, which throws me a little, but she only stops him to tell him there are things about her he doesn't know. John says, "So?" Oh honey, that is so going to bite you in the ass. He takes out the ring. "I will always love you for exactly who you are." Mary leans in to kiss him when there's a sharp rap on Baby's passenger side window. It's YED, but he's pretending he's Samuel, since he's in the meatsuit. "What did I tell you?" He drags her out of the car. John pleads, "Sir, just listen!' He follows them and YED hollers at him to stay away from her. Mary struggles with him, and YED gets physical. Poor, naïve, heroic John can't let that stand. He grabs hold of the man he thinks will be his father-in-law and orders him to take it easy. YED takes it easy all right. He snaps John's neck easily, with just a twist of his hands. Somewhere in the ether, Angelus writhes in envy, and then critiques his artistry. Mary drops to the ground to cradle her beloved's corpse in her arms. YED kicks aside John's legs like they're so much garbage. His eyes turn yellow and Mary looks up and says, "You killed him," so now we know her boys come by their keen powers of observation honestly.
YED crouches to meet Mary eye to eye. "Oh, not just John, sweetie pie. Mommy and Daddy, too." He opens his jacket to reveal the mortal wound in Samuel Campbell's gut. Mary cries out in anger and disbelief while YED taunts her in her loneliness. Mary says, "I'll kill you. I swear. To God." Oh honey, SPOILER: you don't, but you're real instrumental in his death which is dedicated to you, so it's okay by me, if you want to think of it that way. YED suggests they kiss and make up. He'll arrange to have John brought back to life. Mary asks for her parents too, but YED drives a hard bargain. He's offering John and only John, although he sweetens the pot with the idea that she can leave the hunting life for a station wagon/white picket fence/couple of kids existence, devoid of monsters and fear -- he'll see to it. Demons lie. Mary is understandably bitter. "What? And all it costs is my soul?" YED doesn't want her soul, but it's never been spelled out what he does want, so I'll quote him, so you too can wallow in lake vague. "Oh no, you can keep your soul. I just need permission." They size up one another. Finally, Mary says, "For what?" Mary, I don't even think the writers know the answer to that yet. YED loves the soft sell almost as much as the used car salesman. "Mmmm, in ten years I need to swing by your house for a little something. That's all." Deanna Winchester didn't raise no fool. "For what?" YED doesn't want to tell her that. "Relax. As long as I'm not interrupted, nobody gets hurt." He winks and adds, "I promise." I'm sure poor little Mary thinks he's going to do something to her ten years from now. Her parents are dead. John is dead. YED goes for the metaphorical jugular. "Or you can spend the rest of your life desperate and alone." He watches as she weeps. "Mary? It's a good deal. So what do you say?" The yellow Possible-Pinto of Anachronism speeds down the road to John and Mary's inspiration point. How Dean knows to look there, never mind find it, is beyond me, but it takes less handwavium to buy than John dropping Mary off and not seeing her in the house. Dean rounds the last bend and the headlights shine on Mary.