Actress Maddie Banks has landed the female lead in the new hit Broadway show Worst Case Scenario, but her elation is cut short when the son she gave up for adoption 26 years ago shows up, announcing that his adoptive mother has died.

Maddie promises to be present for a home-cooked meal that Arlo offered to prepare for her, but she runs into an old flame (Richard Burgi) after a performance of her show, and decides to hook up with him rather than head home for Arlo's dinner.

When Kathy Griffin looks at a penthouse across the hall, Maddie goes to great lengths to remain the biggest star in her building. Unknown to Maddie, Arlo has been a huge fan of Griffin's for years. Arlo also develops a crush on Griffin's chef, Lucila (Lucila Sola), and convinces Maddie to hire her despite the fact that Lucila is an awful cook.

After Maddie's attempt at throwing a party for Arlo's 27th birthday flops, she and the gang join him and his friends at a karaoke bar. It turns out that Arlo is a really good singer, causing Maddie to go overboard and try to make him a star.

Thelma's ex-husband Duke (George Wendt), a professional pool player, is in town to tell Thelma his womanizing days are over. Maddie finds a ring in Duke's coat pocket, fears that the two will get remarried, and freaks out over the prospect of losing Thelma. But Maddie couldn't be more wrong about Duke's intentions. Meanwhile, a bird gets loose in the apartment, causing Frank to slip and break Maddie's Tony Award.

Maddie has a hard time trying to fire her agent (Jason Alexander), whom she considers useless but can't get rid of because she fears firing people. Thelma must face her fear of identical twin girls who live in the building that creep her out like the children from The Shining, while Frank must face his fear of tunnels. Elsewhere, Arlo is being bullied by a coworker named Ahdoot, but he turns the tables when Ahdoot makes a pass at Lucila.

Maddie's over-the-top attempt to give Arlo a special first Christmas with her is upended when he invites her abrasive mother (Cloris Leachman) as a surprise.

When Maddie encounters the real Madison Banks (Kristen Johnston), a waitress whose audition (and name) she stole over 25 years ago, she asks what she can do to make things right. The real Maddie suggests that they exchange lives for an evening, but she soon kidnaps Frank until the current Maddie agrees to a re-do of the audition in front of the original director.

Maddie hosts a dinner party for Arlo's new girlfriend Melissa (Lindsey Kraft), a graduate student whom he met in the building, and her snooty parents (Geoff Pierson and Valerie Mahaffey) who are both history professors at Columbia. To bone up, Maddie watches The History Channel all night, but the station has programmed a Hitler marathon. Thelma pretends to be Maddie's maid, while Frank goes to pick up Professor Danniker, Maddie's date and "academic buffer" for the evening. The night is a disaster, as Thelma eats some of Frank's "special" gummy candy, Frank has to step in for Danniker, who got drunk and passed out in his limo, and Maddie has to dodge the advances of Melissa's amorous mother. After Melissa insults Arlo's family and friends, he says he is proud to have people in his life who will go to such great lengths to help him.

After Frank irritates Maddie by not putting her name in his "Tony Nomination Pool" with other limo drivers, Arlo wonders how they ever got along. This leads Frank, Thelma and Maddie to recall when the three of them met in the 1980s.

After firing a stagehand named Mickey (John Travolta), Maddie consoles him with a one night stand, but then can't get rid of him. Frank asks Lucila, Arlo's crush, to be his tango partner in a dance competition.

After learning that Arlo is a virgin, Maddie pays her understudy Brittany (Kristin Chenoweth) to seduce him. But things go awry when, after the act, Arlo says he is in love with Brittany and makes plans to spend the rest of his life with her.