New owners Frank Flynn and Mae have taken over the corner bar. Frank recalls his war days in Korea, where he was dubbed "Filet of Seoul" because of his reputation as a womanizer. When Lin, a young Korean man, visits the tavern in search of his American father, Frank braces himself for belated parenthood. However, it soon transpires that anyone in the former 105 infantry division could be Lin's father. As the tavern fills with Frank's old war buddies, Lin's true identity is revealed.
After hearing about a local group of wife swappers, Mae begins to suspect that its members are covertly using The Corner Bar to make contact with other couples. Frank is also drawn into her suspicions. Separately, they make plans to infiltrate the group and expose its activities, but unwittingly find themselves becoming members instead.
The Corner Bar becomes the site of the battle of the bulge. Frank has applied for partner insurance with Mae, but finds that his girth is standing in the way. When he is asked to pay an extra 300 hundred dollars for the premium, Mae insists that he lose weight. Frank then embarks on an excruciating crash diet to drop fifteen pounds.
A diplomat being driven to the airport entrusts Fred with an attaché case. Meanwhile, at The Corner Bar, gangsters Vincent and Albert mistakenly grab Phil's briefcase on their way out. Later, Phil opens the case he believes to be his own and discovers fifty grand in bills. Fred arrives and leaves again, just as the two hoods return for their money. They find that Fred has accidentally taken their case, leaving the diplomat's attaché behind. Vincent forces Frank to lock the bar, and the staff and patrons are held captive until Fred's return. However, the police arrive ...
The police are called to The Corner Bar, where Frank and Mae report a theft. The bar itself has been stolen, and Mae gives the officer a detailed description of the missing mahogany. Later, a phone call comes from a kidnapper, who claims he is holding the bar for $2000 ransom. Frank arranges a meeting with the thief. That night the staff and patrons overpower the culprit. The sudden arrival of The Enforcer, a disguised Meyer, terrifies the thief into returning the bar.
Blanche, Mae's aunt, has been feeling lonely ever since her husband started working a night shift. Frank is persuaded to help by hiring Aunt Blanche as the bar's cook. However, Blanche quickly begins to smother the staff and patrons with irritating motherly advice. One by one, the bar regulars start to leave, vowing not to return until Aunt Blanche herself is gone for good. Frank and Mae must concoct a scheme to make Aunt Blanche quit of her own accord.