After their night together, Helen tells Joe that it was all a big mistake and she goes to New York to marry Davis. While bemoaning his loss with Brian (who has sorrows of his own, when news comes that Alex has left the island for good), Joe comes to realize he has to win Helen back. He follows her to New York and finally catches up to her in the elevator on the way to Davis' penthouse.

The arrival of Helen's elder sister Casey to Nantucket sidetracks Joe's plan to give Helen an engagement ring. What was originally planned to be an evening for two at Lexington's becomes a party of four, with Casey along to catch up with Helen and Brian along to occupy Casey. Then, before Joe can give Helen his ring, Casey gives Helen an even bigger ring as a gift, and Joe's angry frustration brings the night to a halt. He apologizes later that night and gives her the ring, but once again Casey drops in to spoil things. Helen finally stands up to Casey, who then reveals that her husband has left her, and she has no where to go. So Helen invites her to stay with her for as long as she wants.

After Brian's depression over Alex's departure results in a near break-down during a flight, Joe suggests he go see a psychiatrist. Once there Brian makes a partial recovery, but Joe is the one with the true breakthrough, as he realizes that his earlier acceptance of Helen's suggestion of an earlier wedding date may result in trouble for him in the marriage. When confronted, Helen agrees on the original wedding date, until Casey sparks some doubts. Misunderstandings ensue, resulting in the wedding being called off. Meanwhile, Lowell attempts to find a hat that Antonio lost.

After his therapist pronounces him fully recovered from his break-up with Alex, Brian plunges back into the dating world. His efforts at the Club Car yield nothing of interest (despite Antonio's assistance with the "Good Cop, Bad Cop" routine), so he follows the advice of others and starts dating casual friend Joan. That elusive "spark" that is missing from their first three dates finally comes to life when Brian breaks up with her, but the "spark" that was there during their dates is now gone. Meanwhile, Lowell prepares a commencement address for his alma mater and Casey has trouble getting a good haircut.

After receiving $25,000 from the family trust fund, Lowell invests the money in an old wax museum. Despite everyone's doubts, Lowell renovates the museum. but he comes to realize it won't be easy at the lackluster grand reopening of "Lowell Mather's House O' Wax". When news comes of a disastrous fire at the museum, Lowell is determined to start again from scratch.

Joe and Helen just want some time alone with one another, but Brian and Casey continually interrupt them. Brian and Casey decide to surprise them with an engagement party as an apology, but Antonio misinterprets an overheard conversation and believes Brian to be sleeping with Casey. When she hears about it, Helen drags Joe to the party site well before they are expected.

To pay off a $1500 IRS fine, Antonio becomes the driver/errand boy/personal assistant to Gavin Rutledge, a businessman visiting Nantucket for a week for a real estate deal. Uncomfortable at seeing Gavin dating Casey, Antonio faces a major dilemma when he finds out Gavin is married. At the cost of his job, Antonio tells Casey about Gavin, and Casey shows her gratitude by giving Antonio a jewelry gift she received from Gavin. Meanwhile, Joe is Irked that Brian had an erotic dream about Helen.

The return of 9th grade English teacher Laura Jenkins to Nantucket reawakens the Hacketts' schoolboy crushes. For Brian, fantasy becomes reality when he spends the night with her, but to his embarrassment he doesn't perform. Meanwhile, Roy deals with a con man interested in marrying his mother for her social security check.

When Helen and Casey's mother arrives on Nantucket, Helen isn't sure which sister her mother came to see. And when she finds out her mother gambled away the $10,000 for her and Joe's wedding, she is convinced that Casey has always been the favorite of the family. Meanwhile, Fay and Roy split a ticket to a Barbara Streisand concert; Antonio adopts Deedee as his own mother; and Lowell and Brian stuff themselves on Deedee's food in an attempt to see who can out-eat the other.

To counteract Roy's Aeromass promotions, the Hacketts woo famous astronaut Ace Galvin as a celebrity spokeman for Sandpiper. Joe and Brian soon discover that Ace is as charming and persuasive in public as he is irratating and annoying in private life. Any hopes of signing him up are dashed when Roy beats them to the punch, but Roy quickly discovers just how obnoxious Galvin can be.

On Christmas Eve, new air traffic controller Bob snaps when Antonio buys Helen's last jelly donut, pulling out a gun and taking Antonio hostage. Matters for Antonio only get worse when it is revealed that his new girlfriend is also Bob's wife. Joe is eventually able to talk Bob into surrending his gun, but the others are not very appreciative of the means by which he does it.

When Sandy Cooper returns to the island, Joe fears yet another bizarre encounter with the obsessed woman. She tells him it was all a practical joke, and he believes her until a stop at Helen's house becomes Sandy and Joe's wedding day. Meanwhile, Fay forces the old '70s wardrobe of one of her dead husbands onto Antonio, and Lowell tries life as a vegetarian.

With nothing to do one Saturday night, Joe and Helen start socializing with a new couple on the island, the Tuckers. Their initial trepidation is soon forgotten in all the fun, but the Tuckers quickly tire of their needy counterparts. Meanwhile, Brian and Casey start hitting the singles hangouts together and Antonio becomes Lowell's "hands" when Lowell injures his working on the cab.

When Roy flies in a mail-order bride from Russia, Helen tries to convince Roy and Anya that this marriage should never be, but both ignore her. Anya's resolve is weakened by a chance encounter with another man, and the sight of her weeping just moments before their wedding convinces Roy to free her from his commitments to him. Meanwhile, Fay convinces Lowell to pretend to be her lover to impress her soon-to-arrive friends, but Lowell insists on cramming and it finally gets to Fay who calls the whole thing off just moments before they are to arrive.

Struggling to agree on wedding plans, Joe and Helen decide to crash another couple's wedding to check out a place. Unfortunately their fighting infects the newlyweds. At the airport later, seeing the newlyweds about to take seperate honeymoons, Joe and Helen try to right their wrongs and bring the newlyweds back together. Meanwhile, Lowell and Antonio train for a Polar Bears competition.

The Gang make preparations for the upcoming Siasconset High School reunion, but the events of the reunion are not what anyone expects.

After receiving the news that he might be the father of Sara's little boy, Jason, Joe is advised by Roy to keep quiet on the whole affair, but Joe's guilt forces him to tell Joe and Helen. Meanwhile, Lowell questions his choice in careers and Antonio struggles to make Casey his valentine.

When Fay decides to retire, Joe and Brian hire Casey to replace Fay at the counter. To the Hacketts' surprise, Casey works wonders for their business. When Fay asks for her old job back, the brothers face a predicament. Rather than fire Casey, they decide to keep both at the counter, and sparks soon fly between the women.

Brian's excitement over appearing on a talk show is dampened when his ex-girlfriend Alex also appears. After bitter words on and off the screen, the two sleep together, but Brian decides to end things.

Lowell's innocent birthday gift to Casey lands him a show at an art museum when Casey shows off the gift to a museum director. Determined to launch both their careers in the art world, Casey relentlessly pushes Lowell's artistic abilities to the limit to try and meet the show's deadline, but eventually gives up after discovering how stressed Lowell becomes. Meanwhile, Brian's efforts to finish a roll of film for Joe and Helen are not appreciated, as the prank ends up in the hands of Helen's parents.

As the wedding draws near, Brian struggles to come up with a gift idea for Joe and Helen. He finally hits on the idea of making a video for them, and goes about capturing everyone's memories of their relationship on video.

Carlton's ill health becomes a boon to the gang when Carlton's nephew Lewis invites them over to Carlton's house to start selling off the old man's items. Joe and Helen have an eye for the house itself; Brian drools over a classic muscle car; and Roy looks for furniture. But all is for naught as Carlton's health makes a swift turnaround.

When Helen discovers that she and Antonio are still married (by finding papers under her cash register), she turns to Roy for help. He convinces her she needs to fly to Mexico over the weekend to get a quickie divorce, but that means sending Joe out of town on a weekend fly fishing trip. But Helen's plan are strained when Antonio brings in a priest for an annulment and Joe's flight is delayed.

When Antonio's cousin Dominic and his fiancée Teresa visit Nantucket, Antonio finds himself struggling to ignore his feelings for Teresa. He succumbs to temptation during supper at his apartment, after Teresa voices concerns over problems with her relationship, but he ultimately helps Dominic win her back. Meanwhile, Helen's side of the family outshines Joe's when the wedding gifts start to arrive.

The night before the wedding, Helen warns Joe not to have too wild of a bachelor party. But it's Helen who ignores her own advice in a wild bachelorette party, while Joe suffers through the worst bachelor party Brian's ever thrown. Later that night, after the guys return, Casey accidently slips into bed with Brian, and neither feels like leaving the other's company.