When a bachelor party and a bachelorette party cross paths in Vegas, only the best man and the maid of honor can save their friends from a night of epic "mistakes."

It's Derek's bachelor night and he and three friends set off for Las Vegas for the festivities. There they meet Casey and her three friends: she's there for her bachelorette party. They're all there to have some fun but nothing will prepare them for what lies ahead.—grantss