Stu (Ed Helms) is getting married. Along with Doug (Justin Bartha), Phil (Bradley Cooper), and his soon-to-be brother-in-law Teddy (Mason Lee), he regretfully invites Alan (Zach Galifianakis) to Thailand for the wedding. After a quiet night on the beach with a beer and toasting marshmallows by the camp fire, Stu, Alan and Phil wake up in a seedy apartment in Bangkok. Doug is back at the resort, but Teddy is missing. Additionally, there's a monkey with a severed finger, Alan's head is shaved, Stu has a tattoo on his face, and they can't remember any of it.