All the couples are back for a vacation in viva Las Vegas. Where the old saying goes, "What happens in Vegas...stays in Vegas." One of the lucky couples from the last film is getting married, so each of them split off into gender groups. Each gender determined to have the time of their lives before the big wedding. However, things go haywire, as this may turn out to be one vacation they may not soon forget.

Carly finally meets the guy of her dreams. Everything seems to be perfect between them, as he's handsome, rich and charming. However, the only downside is that he's married. After finding out about his marriage, she decides to cut all ties with him completely.

However, that doesn't stop his own wife from seeking her out for answers. Through a series of events the two form an unlikely bond, and they even find out about another one of Mark's mistresses.

Now, the three of them conspire together to get even with the three time cheating son of a b****!