Trigger the Gala Event

 is a quest in the Fallout: New Vegas add-on Dead Money.

Quick walkthrough

 * Assuming you have put all of your companions (Dog/God, Christine, and Dean Domino) into place you must then find the bell tower. I found it because I put Dog/God into place last then from the switching station in Salida Del Sol Follow your map marker to the tower. You will have to fight numerous Ghost People on the way and inside the tower.
 * After triggering the Gala Event, Ghost People will pour into the courtyard below the Bell Tower. You will have to fight your way back.