Movie star Vincent Chase, together with his boys Eric, Turtle, and Johnny, are back - and back in business with super agent-turned-studio head Ari Gold on a risky project that will serve as Vince's directorial debut.

Angelenos Doug Billings and Tracy Garner are about to get married. Two days before the wedding, the four men in the wedding party - Doug, Doug's two best buddies Phil Wenneck and Stu Price, and Tracy's brother Alan Garner - hop into Tracy's father's beloved Mercedes convertible for a 24-hour stag party to Las Vegas. Phil, a married high school teacher, has the same maturity level as his students when he's with his pals. Stu, a dentist, is worried about everything, especially what his controlling girlfriend Melissa thinks. Because she disapproves of traditional male bonding rituals, Stu has to lie to her about the stag, he telling her that they are going on a wine tasting tour in the Napa Valley. Regardless, he intends on eventually marrying her, against the advice and wishes of his friends. And Alan seems to be unaware of what are considered the social graces of the western world. The morning after their arrival in Las Vegas, they awaken in their hotel suite each with the worst ...