At the party John Gilbert told Damon that he knows about the tomb and the vampires, so Damon killed him. A few minutes later John Gilbert returned very much alive because he had a ring, the same as the one that Alaric Saltzman has. John took his ring from his brother, back in the 1990s and gave his to Isobel, who gave it to Alaric before she left town.
While Stefan and Elena were dancing, they accidentally ran into Duke, who insulted Elena. Stefan made him apologize by compelling him. Later Duke provoked Stefan and Stefan almost killed him, but Elena came, so he ran away. Stefan also touched Kelly Donovan's blood and tasted it afterwards.
Also, Tyler and Kelly started making-out and Matt saw them. He and Tyler got into fist fight and Matt had lost horribly and had blood on his face. Mayor Richard Lockwood told Tyler to never embarrass his family again. Matt stays mad at Tyler until Founder's Day near the end of the celebration.
After the event Matt told his mom that he wants her to leave the house because of what happened.