Stu (Ed Helms) prepares for his wedding in Thailand, reluctantly inviting his friends Phil (Bradley Cooper), Doug (Justin Bartha), and the unpredictable Alan (Zach Galifianakis). After a seemingly innocent night out, they awaken with no memory, a missing groom's brother Teddy (Mason Lee), and chaos surrounding them. As they retrace their steps through Bangkok's wild nightlife, hilarity ensues, leading to unexpected revelations and a race against time to save the wedding.