After Dennis and Dee's gold-digging mother dies from a botched plastic-surgery operation, Dee and Frank scheme to get their name in the will, while Dennis inherits the house and makes plans for a party mansion.
Charlie, Mac, Dennis and Dee are held hostage in the bar by a revenge-seeking Liam McPoyle along with his dim-witted brother, Ryan, and his ugly, deaf and dumb cousin, Margaret, who subject the nihilistic quartet to various torture and mind games, while Frank hides out in the air ducts while searching for a will to a relative of his and decides to take matters in his own hands to end the hostage situation.
Dee discovers that her old high school friend "Fatty McGoo," the only girl in school who was a bigger loser than she was, is now a successful fashion designer. She and Dennis compete to create dress designs while Frank and Mac open a sweatshop to manufacture Dennis' dresses.
A corporate chain offers to buy the Paddy's Pub, leaving Dee and Charlie unemployed and forcing them to find jobs at another restaurant, where they abuse their positions and take advantage of the manager, who is Dee's friend.
While Dennis and Dee try to figure out if the rapper Dee is dating has a mental handicap or not, Charlie, Mac, and Frank try to start their own band without knowledge of how to play musical instruments.
Dennis is angry because he's being mistaken for a fat guy rather than the sex offender who moved next door to Charlie. Meanwhile, Mac's father is released from prison and he and Mac have some catching up to do.
After stumbling upon a kilo of cocaine, the gang is forced to pay off a $25,000 debt to the mob. Mac becomes a mob informant, while Frank pimps out Dennis as an escort at the local country club. Charlie stumbles upon an opportunity to sell illegal narcotics.
While paying off their debt to the mob, Charlie and Dee try to find a way to make fake cocaine in order to fool them, while Dennis ranks in thousands of dollars being pimped out at the local country club. Mac realizes his position as a mob informant isn't being utilized to its full potential.
Dee and Mac become Guardian Angels and clean up the streets when a bum starts using the alley behind the bar to masturbate. Meanwhile, Dennis, Charlie, and Frank impersonate police officers in order to get preferential treatment.
After Charlie accidentally puts Paddy's Pub up for 1st prize in a local dance competition, Frank makes the gang participate in the contest. Here, they form alliances and try to cheat the other contestants, as well as themselves, out of first place.