Praising his up and coming marriage to Tracy Garner (Sasha Barrese), Doug Billings (Justin Bartha) goes with his closest companions Phil Wenneck (Bradley Cooper), Stu Price (Ed Helms).
And Tracy’s sibling and Doug’s future brother by marriage Alan (Zach Galifianakis) to Las Vegas in Alan’s dad’s vintage Mercedes-Benz for a lone wolf gathering, staying at Caesars Palace, where they unwind in the room and go to a club and celebrate with a couple of beverages on the lodging roof.
The following morning, Phil, Stu, and Alan stir to discover they have no memory of the earlier night, and Doug is no place to be found. Stu is forgetting a tooth.
Their lodging suite is in confuse, a tiger is in their restroom, a chicken in their parlor, and an infant is in the wardrobe, whom they name “Carlos”.
They discover Doug’s sleeping cushion skewered on a statue outside of their inn and when they request their Mercedes, the valet conveys a LVPD police cruiser.
Taking after hints to their steps, the trio venture out to a clinic where they find they were medicated with rohypnol (“roofies”), bringing on their memory misfortune, and that they went to the doctor’s facility from a church.
At the sanctuary, they discover that Stu wedded a stripper, Jade (Heather Graham), not withstanding having a long haul association with his dastardly mate, Melissa (Rachael Harris).
Outside the church, the trio are assaulted by hoodlums, saying they are searching for somebody.
They escape and visit Jade, finding that she is the mother of the infant, whose genuine name is Tyler, before being captured by the police for taking the police cruiser.
Having been informed that the Mercedes has been seized, the trio is discharged when they unknowingly volunteer to be focuses for a taser show.
While driving the Mercedes, they find an exposed Asian man in the storage compartment who assaults them and escapes. Alan admits that he sedated their beverages to guarantee they had a decent night, thinking the medication to be delight.
Coming back to their manor, they discover Mike Tyson, who requests the trio to furnish a proportional payback to his chateau promptly.
Stu drugs the tiger with the remaining rohypnol, and they drive towards Tyson’s home in the Mercedes.
Nonetheless, the tiger stirs and assaults them, ripping at Phil on the neck and harming the auto’s inside.
In the wake of pushing the auto whatever remains of the path to the house, Tyson demonstrates the trio footage of them at Tyson’s home to help them place Doug. While driving, their auto is deliberately t-boned by an alternate vehicle.
The travelers of the culpable auto are uncovered to be the criminals from the house of prayer, and their supervisor Leslie Chow (Ken Jeong) – the stripped man from their trunk – blames the trio for both abducting him and taking $80,000 of his cash that was in his handbag.
As the trio tries to deny this, Chow says he has their companion, debilitating to execute the companion if Chow’s cash is not returned.
Uninformed of the area of Chow’s $80,000, Alan, with assistance from Stu and Jade, utilizes his insight into card numbering to win $82,400 playing Blackjack.
They meet with Chow and trade the cash, just to find that “Doug” is an African-American street pharmacist (nicknamed “Dark Doug” by the trio), who accidentally sold Alan the roofies.
With the wedding set to happen in 5 hours, Phil calls Tracy and advises her that they can’t discover Doug.
After a discussion with “Dark Doug” (Mike Epps), Stu acknowledges where Doug is. The trio flies out once again to their inn where they discover a ridiculous and sunburnt Doug on the top.
Stu, Phil, and Alan had moved him there on his bedding the prior night as a useful joke, yet expeditiously overlooked where they exited him.
Doug’s sleeping pad had been tossed onto the statue by Doug himself, trying to motion for help. Before leaving, Stu makes courses of action to go out on the town with Jade the accompanying week.
With short of what four hours prior to the wedding and with no flights to L.a. accessible, the foursome races home, wherein Doug uncovers he has ownership of Chow’s unique $80,000.
Notwithstanding their late landing, Doug and Tracy are hitched, and Stu indignantly says a final farewell to Melissa in the wake of having become drained of her controlling his life.
As the gathering closures, Alan finds Stu’s computerized cam itemizing the occasions they can’t recollect, and the four consent to take a gander at the pictures together before erasing the confirmation of their adventures.