Karen is unaware that her presumed-dead spouse---the never seen Stan---is actually alive. Her friends are reluctant to tell her because she's now involved with the enigmatic Malcolm (Alec Baldwin).
Stan's return rattles Karen, who feels “lied to.” Will offers solace---sort of. Meanwhile, Grace gets a rep as a homophobe on Jack's TV talk show, thanks to injudicious editing that she seeks to set straight in no uncertain terms.
Andy Richter guest stars as Grace's blind date, a cheery though clueless goof who's an old pal of Karen's tempestuous beau Malcolm (Alec Baldwin). Elsewhere, Will takes swimming lessons---from Jack.
Richard Chamberlain appears as a sarcastic, reclusive buttinsky who figures in Grace's 10th annual trivia game. In other events, Stan reappears---sort of---in a very steamy steam room, where he's confronted by Malcolm, Karen's new love.
Jason Biggs plays Jack's new flame, a flighty egotist who had 15 minutes of TV fame as a preteen when he fell into a hole. Now he's a participant in Jack's corny carnival, where Grace is a reluctant date for Malcolm.
Harry Connick Jr. reappears as Leo, Grace's itinerant ex, whom she beguiles anew on a plane trip. Meanwhile, Karen's captivated by her new maid, a shrewd British matron (Millicent Martin) who takes an instant disliking to Jack.
Will is thrilled to help Jack look for another apartment, but after getting involved in an effort to help two gay penguins stay together at the zoo, he has second thoughts about his friend's move. Beverley: Leslie Jordan. Rose: Traci Lords.
After another visit with her domineering mom (Debbie Reynolds), a frazzled Grace gets advice from Jack on how to deal with her. Meanwhile, on the first day of his new job, Will chases after a slumlord: Karen. Gerald: Sunkrish Bala.
During a Christmas celebration at Marilyn Truman's house, Will, Grace, Jack and Karen debate about whether Will's “artistic” young nephew is gay. Also, Grace tries to comfort Will's brother (Steven Weber), whose divorce was just finalized. Marilyn: Blythe Danner.
Grace dresses like Maria for a sing-along screening of “The Sound of Music,” but Will, her Capt. Von Trapp, winds up at the wrong theater, where he meets a cute stranger (Taye Diggs). Meanwhile, the gang wonders how to solve a problem like Karen after she gets herself into trouble with theater management. Rosario: Shelley Morrison.
Karen celebrates her birthday with some of New York's crème de la crème, but the festivities turn sour when she ends up crammed in the bathroom with Grace, Will and Jack, who have all embarrassed themselves at the party. Matt Lauer guest stars.
Will gives Grace a guilt trip when his former boss (Lily Tomlin) offers her a lucrative decorating job that conflicts with a job she has planned at a nursing home. Meanwhile, Jack's dying of curiosity about a “forbidden room” in Karen's mansion.
Will and Grace are shocked when their seemingly happily married friends announce over dinner that they're splitting up. Then Will gets another jolt when their waiter turns out to be his ex-boyfriend (Bobby Cannavale), who was once a cop. Meanwhile, Jack wants to be like Oprah and help the underprivileged.
Will, Karen and Grace journey to Los Angeles, where Jack is set to receive an award for “Best Local Cable Gay Talk Show Host.” While Grace becomes starstruck in the celebrity-saturated city, Will chances upon his friend James (Taye Diggs) and learns he's a Canadian who's worried about being deported.
As Grace prepares for her green-card marriage to James (Taye Diggs), she frets that Karen is going too far by organizing an overly lavish wedding spectacle that includes a performance by Hall and Oates. Later, as the ceremony begins, Grace has a strange physical reaction to the proceedings.
Grace reluctantly decides to tell Leo (Harry Connick Jr.) that she's pregnant with his child. Meanwhile, a blissful Will settles in with James (Taye Diggs)---until he discovers something unexpected about his new beau; Jack plans to report on every second of Grace's pregnancy for his talk show.
While hanging out in a bar, Jack proudly introduces Will to his hot new boyfriend (Shawn Christian), who promptly makes a pass at Will while Jack isn't looking. Meanwhile, Grace's “liberal guilt” causes her to hire an incompetent Iranian assistant (Shohreh Aghdashloo). Benji: Brian Setzer.
Britney Spears guest stars as Amber-Louise, a vitriolic right-winger who's brought in to cohost Jack's talk show after a conservative conglomerate takes over OutTV. But Jack soon learns that Amber-Louise may harbor a secret. Meanwhile, Karen hires a surrogate mother (Wanda Sykes) to carry her baby.
Will gets upset when his parents (Sydney Pollack, Blythe Danner) give Grace his boyhood blanket, resulting in a family squabble that escalates with devastating consequences. Meanwhile, Karen pushes an unemployed Jack to pursue his acting dream.
On the day of his father's funeral, a grieving Will can't let go of the terrible argument the two of them had right before his dad passed away. Meanwhile, Grace's anxiety over impending motherhood worsens after she clumsily explains death to Will's young niece. Vince: Bobby Cannavale. Marilyn Truman: Blythe Danner. Sam: Steven Weber. Tina: Lesley Ann Warren.
As Will rekindles his relationship with Vince (Bobby Cannavale), Grace wonders if he will be there for her once the baby arrives. Meanwhile, Karen's marriage is in trouble, but she finds little comfort from Jack, who's preoccupied with his new TV show.
Vince (Bobby Cannavale) has a surprise for Will that causes him to question his commitment to Grace and the baby. Meanwhile, the gang learns that Karen has a long-lost sister (Bernadette Peters); and Jack gets some disturbing news when his new TV show debuts. Josh Lucas also guest stars.
In Part 1 of the two-part series finale, Grace has a dream in which she imagines what her future would be like with Will.
In the conclusion of the series finale, Grace, Will, Jack and Karen see their futures evolve, and where they end up is quite surprising.