Grace's accidental run-in with Noah, a curmudgeonly man she follows on Twitter, hints at a possible new love interest. Jack wants to look younger before meeting Estefan's family on Skype but makes a terrible first impression after overdoing the numbing cream before his facial procedure. Meanwhile, Will helps Karen protect the intellectual property rights of her most prized possession.
Will, Grace, and Jack are upset when they discover they've been too preoccupied with the changes in their own lives: Will teaching law at Columbia, Grace running for president of the New York Interior Designers Society and Jack's new relationship with Estefan to even notice Karen has not been seen in days - ever since her husband found out about her affair with Malcolm.
Will and Jack visit Jack's grandson, Skip, in Texas to watch him perform at his church's talent show. But when Jack learns Skip plans on singing "Diamonds Are a Girl's Best Friend", he becomes afraid for his grandson's safety. Karen tags along to check out the portion of the border wall she sponsored, only to discover that Beverley Leslie has claimed it as his own. Grace and Noah try to figure out if something is wrong in their relationship because their attempts to have sex have failed.
Will and Grace discover old letters written to each other from their college days, and decide to read them together. But reminiscing about the past turns ugly when a major bombshell is revealed in one of the letters. Meanwhile, when Karen announces she'll never fall in love again, Jack channels Rosario - or does he? - to convince her it's never too late to find love.
Grace joins her father on a road trip, and a secret from her past is finally revealed, causing father and daughter to address something that will change their relationship forever. Meanwhile, Will, Karen, and Jack celebrate Jack's engagement at a gay bar run by legendary drag queen Miss Coco Peru. When it's revealed that Jack has chosen both of them to be his best man, Will and Karen have a lip-sync monologue throwdown to determine who truly deserves the coveted title.
Will discovers that Noah has a child he hasn't told Grace about, but is now sworn to secrecy. Karen and Jack's relationship is tested when she fires him from the play she's producing and replaces him with Jon Cryer.
Grace unintentionally meets Noah's daughter Katie; Will's mom Marilyn visits after the death of her beloved dog, but doesn't get the emotional support she expects; Jack argues with his rec center boss, Theo.
Best friends, Will, who is a gay lawyer, and interior designer Grace, share an apartment and are constantly in each other's business. Stirring the pot of melodrama is Grace's "employee", Karen, and Jack, Will's flamboyant friend.
Will, Karen and Jack unknowingly take a hallucinogenic drug, which causes Will and Jack to wonder if they're each other's soul mate and has Karen giving her last "performance" as Mrs. Stanley Walker. Meanwhile, Grace is shocked when her high-powered client takes up with her sister Janet.
Will and Grace's plan to win over Will's new Columbia department head goes awry when he drops dead in their apartment - and they use his phone to text his full recommendation of Will. Karen and Estefan's dislike for each other puts Jack in full damage control mode when he must keep them separate at his birthday dinner.
When Will discovers Karen's estranged stepdaughter Olivia is a student in his law class, he attempts to solve their issues with a mock trial. Grace and Jack go on a diet together, but giving up their eating habits proves harder than anticipated.
Malcolm enlists Grace to help him win back Karen's affections. Will's flirtation at work lands him in an ethical dilemma. Jack's passion for performing is reignited by a chance encounter with Zusanna, the sister of his former acting teacher.
Will gives local newscaster McCoy Whitman a second chance and, with the help of Jack, finally gets to know the man behind the newsman. Grace's campaign for Design Guild President hits a snag when the deciding vote comes down to her old nemesis, Val. Karen acts as Grace's campaign manager, and attempts to secure Val's vote by any means necessary.
Jack's insistence that Will be nicer to Estefan backfires; Grace unknowingly knocks over a prominent figure. When Karen discovers Noah plans to hug off the main character of her favorite romance novel, she forces him to rewrite the story.
After her dad, Martin, is rushed to the hospital, Grace is shocked when he refuses a transfusion of Will's blood. Will's mom, Marilyn, uncharacteristically takes Martin to task. Karen's demands cause Jack to uninvite her to his wedding.
When both of their boyfriends ask to move in, Will and Grace use each other as an excuse to get out of it. A snowstorm traps Karen at the office and Jack in an elevator, where he reunites with old flame Drew and tests his commitment to monogamy.
Jack realizes he lost 13 gold coins he's supposed to give Estefan at their wedding to avoid a curse. Will is concerned that Grace is the only one compromising in her relationship with Noah. Karen shows up at a dinner party with her new date, Nikki.
Jack and Estefan's romantic wedding in Spain takes a detour when their flight is cancelled, forcing them to get married at the airport by their friend Miss Coco. McCoy's big job offer in London has Will worried about engaging in a long-distance relationship. While dealing with doubts about her current relationship, Grace meets a charming guy at the airport who inspires her to make an impulsive decision. And advice from Smitty makes Karen reconsider her commitment to Nikki and her own sexual orientation.