We flash way back to the 11th century on this episode of The Vampire Diaries and learned about the Brotherhood of the Five. They have tattoos that expand with each vampire they kill and Connor got his after telling a fellow soldier in Iraq that he had intense urges to kill vampires.
When that soldier died, the tattoo appeared on Connor.
Klaus held him captive this week and Jeremy drew the map that leads to the "ultimate weapon" that The Five were seeking: A CURE for being a vampire!!! Stefan wants it to save Elena, while Klaus wants it to make Elena human again so he can take her blood and make hybrids. They agreed not to tell anyone about the cure.
Rebekah, meanwhile, was daggered because was in love with an original Five member and would get in the way of Klaus and Stefan tracking down his sword, which holds the key to the map. It's confusing stuff.
In the end, Connor escaped and we learned he's working with Professor Shane, who is serving as a mentor for Bonnie at the local college.
Elsewhere, Elena nearly lost control at a frat party, drinking human blood and dancing closely with Damon.