Using clues to retrace their steps, the trio travel to a hospital where they discover they were drugged with Rohypnol ("roofies"), causing their memory loss, and that they came to the hospital from a chapel.
At the chapel, they learn that Stu married a stripper named Jade, despite being in a long-term relationship with his girlfriend Melissa.
Outside the chapel, the trio is attacked by gangsters saying they are looking for someone.
They are then arrested by the police for stealing the police cruiser.
After being told that the Mercedes has been impounded, the trio is released when they unknowingly volunteer to be targets for a taser demonstration.
While driving the Mercedes, they discover a naked Chinese man named Leslie Chow in the trunk.
Chow jumps out of the trunk, beats the trio up with a crowbar and flees.
In the follow-up to the record-breaking hit comedy The Hangover, Phil (Bradley Cooper), Stu (Ed Helms), Alan (Zach Galifianakis) and Doug (Justin Bartha) travel to exotic Thailand for Stu's wedding. What happens in Vegas may stay in Vegas, but what happens in Bangkok can't even be imagined.
With the memory of Doug's nearly disastrous bachelor party in Las Vegas still fresh—or at least well-documented—Stu is taking no chances.
He has opted for a safe, subdued, pre-wedding trip brunch, with pancakes, coffee..no alcohol. Two nights before the big day, at a fabulous resort in Thailand, Stu relents.
To celebrate his upcoming marriage to Tracy Garner, Doug Billings travels to Las Vegas with his best friends Phil Wenneck and Stu Price, and Tracy's brother Alan, in Doug's future father-in-law's vintage Mercedes-Benz.
They spend the night at Caesars Palace, where they relax in the room before celebrating with a few drinks on the hotel rooftop.
The next morning, Phil, Stu, and Alan awaken to find they have no memory of the previous night, and Doug is nowhere to be found.
Stu's tooth is in Alan's pocket, their hotel suite is in a state of complete disarray, a tiger is in their bathroom, a chicken in their living room, and a baby is in the closet, whom they name "Carlos".