It's his bachelor bash, his one final night to be a wild single guy, but Paul (Jason Lee) isn't exactly the life of the party. Instead, he's determined not to do anything he can't live with later -- or tell his fiancee, Karen (Selma Blair). That's why it comes as such a shock when the phone rings the next morning and he wakes up to discover a lovely stranger named Becky (Julia Stiles) in bed next to him with no clothes on.

Worse: His mother-in-law-to-be is the one who is calling.
Even worse: She tells him Karen is on her way over.

Paul zooms into frantic action, shooing Becky out the door and desperately trying to rid the apartment of any evidence of wrongdoing - even though he can't remember doing anything wrong. When Karen does arrive and asks him how the bachelor party went, Paul tells a teensy lie to cover up what may or may not be the truth. That teensy lie turns into a bigger one, and soon Paul's life is a series of comical misunderstandings. Paul gets trapped in an ever-escalating comedy of errors with no apparent way out - except up the aisle.

When a guy decides he's ready to make a commitment, how does he know he's making the right one? It's amazing how much can change because of one little thing - A Guy Thing.