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.