It's Kol on the other end of the line. He tells Klaus that Elena and Jeremy have been plotting to kill him. Kol assumes Klaus is in on it, and won't believe otherwise. He threatens to cut of the Germ's arm and kill Elena for the hell of it. "Then I'm coming for you." Elena appears at the top of the stairs and fires the crossbow at Kol. It's a red feathered arrow and I can't help if she got it from Susan Pevensie.
Back at Mossy Manse, Klaus throttles Damon and demands to know what's going on -- what Stefan and Elena are planning. Damon swears he doesn't know anything, but Klaus turns on the compulsion eyes and demands to know what Damon knows. Damon again says he knows nothing about any plan. He very well could be telling the truth. In fact, that's what I'd expect. That's neither here nor there. The point of this scene was made early in the episode, when Stefan brought Damon some water. Oh sure, it's in a bottle, but the bottle is label free, so it's probably been washed and filled up with tap water. Interim Dad spiked the town water supply with vervain. When Klaus leaves, he compels Damon to stay there until he returns. As Klaus storms out, Damon does his best robot impression and repeats Klaus's command. He looks over at the water bottle to make sure we're keeping up, and then walks out.
School. When Stefan returns with a bottle of booze he pilfered from the faculty lounge, I feel sorry for the Ghost of Alaric, who isn't even in this episode. Stefan finds Rebekah dancing to Bon Jovi and there's some sentimental conversation about Lexi, which turns to talk about Elena and how both women made him better than he'd be on his own. When Stefan proclaims that the thing with Elena is over, his eyes betray him, and Rebekah says his expression is exactly the reason she doesn't let herself care. Stefan knows she's fronting and calls her on it. When they hear a balloon pop, Stefan jumps. Rebekah tells him she'll protect him if Kol decides to crash their private party and reveals she's got the dagger hidden in her boot. With the promise of a new idea, Stefan encourages Rebekah toward the hallway, then texts Matt with the dagger intel and an order to get to the school.