Doug is getting married. His two best friends and his new brother and law accompany him on a bachelor party to vegas. Along the way, they suffer from such a bad hangover that they can't recall the events that happened the night before. Doug ends up being separated  form the group and Allan, Phil, and Stew can't seem to find him. As their memory starts to increase, they gain clues as to where Doug might be. They revisit the places that they went to the night beforehand, and eventually relocate Doug. With the heavy drinking, and use of drugs, the bachelor party quickly went from fun to dreadful. As time went on, they gained their perspective back as the alcohol and drugs wore off.