Tommy is still reeling from his breakup with Alissa, but Sally and Harry convince him that if he can find an excuse to go over to her house, he can persuade her to watch a movie with him. When the pair leave the house together, however, Strudwick is suspicious and confronts Dick. Mrs. Dubcek suggests that they could have eloped, so Dick and Strudwick rush off to track them down before there's a baby on the scene, managing to accidentally abandon Mary in the process. Meanwhile, Tommy has rented a scary movie to watch with Alissa, in the hope that it might bring her into his arms, but Sally and Harry decide to show up and make it more real.

Dick and Mary decide to go on a double date with Sally and Don, but things start to become uncomfortable when Dick and Sally begin talking incessantly about how good their other half is in bed. The next day Dick and Sally come to realize that neither Mary or Don said anything about how good they are, and immediately worry that they aren't. Meanwhile, in a food store, Mary and Don run into each other and, consumed by what they'd heard about each other in bed, share a kiss. Elsewhere, Harry and Tommy follow in the footsteps of Jack Kerouac and take to the open road.

The Solomons visit a parallel universe, in which they are living in New York City, where Dick is a highly regarded attorney, Sally writes a sex column and Harry is President of NBC, while Tommy is a star on Saturday Night Live. Despite this, Dick is unhappy because he cannot find Mary; however, upon entering a basement bar he discovers her, a failed actress-turned torch singer who has renamed herself Kiki Lyle. Meanwhile, Sally discovers that Don is the Mayor of New York, and that she isn't his girlfriend, but his mistress.

Dick takes Mary up to his penthouse and wines and dines her, but she tells him that she doesn't believe in true love anymore, no matter how hard he might try to persuade her otherwise. Meanwhile, Sally isn't happy being second fiddle to Don's wife so she asks him to break up with her. Don, however, wants to run for president and so refuses, so Sally breaks up with him; while at NBC, Tommy's huge ego and demand for a high pay on Saturday Night Live leads Harry to fire him.

Tommy is looking for a college to attend and Dick steers him away from the big names such as Harvard and tries to convince him to attend Pendelton instead. Upon taking one of Dick's classes, however, Tommy decides that Dick is a lousy teacher and that he would rather look elsewhere. Outraged, Dick orders Tommy to go to Pendelton. Meanwhile, Sally is concerned that Don isn't listed one of Rutherford's ten most powerful men and so she gets him a job working for one of them.

The Solomons' say goodbye to Tommy as he goes to college, but Dick soon begins to miss him and attempts to convince him to come home. Tommy, however, is enjoying college life and doesn't want to, so Dick convinces him to pull an elaborate freshman prank to gain himself popularity, but really in the hope that Tommy will be expelled. Meanwhile, Sally and Harry are interviewing candidates for Tommy's replacement and although their best candidate appears to be a woman called Christie, when a handsome man named Bryce walks through the door, Sally hires him on the spot.

After hearing the crowd sing The Star Spangled Banner at a baseball game, Dick realizes that humans are passionate about their country of origin and attempts to become more American, only to discover that he actually has a Canadian passport. Meanwhile, the other Solomons' work on the basis that all Americans are equal, and start an equality system in the house, putting Harry in charge, who makes everybody wear the same uniform and rations household items, until Tommy begins to fear that they are losing their individuality.

When Dick accompanies Mary on an archeological dig, he is disappointed when the only thing he finds is a small pointed rock. Mary realizes, however, that it is an ancient spearhead and becomes upset, revealing that she has never found anything before. So, in order to make Mary happy, Dick steals a ceremonial wedding moon that was found the previous day and lays it for Mary to find. Meanwhile, the Rutherford Garlic Festival is on and Sally, Harry and Tommy decide to turn their attic apartment into a hotel, but things soon become hostile between them as they attempt to make their 'hotel' good enough to get a four star rating in the Crown Travel Guide.

After playing assistant to a magician at a child's birthday party, Dick decides to himself become a magician, with Sally as his assistant. They become a huge success, performing shows night after night at a local club, but show business soon starts to eat away at their offstage relationship until they hate each other. Meanwhile, Mary joins a defense class after being mugged in the park, while Harry joins the class as the man in the padded suit that everyone attacks.

Dick and Mary visit a psychic together, who claims that the pair are from two different worlds and predicts that Dick will one day up and leave Mary. Horrified at this news, Dick decides to find a replacement boyfriend for her, settling on a man called Gary; who thinks he's actually being offered Dick's position of physics professor. Meanwhile, Sally and Harry decide that if the psychic really knows that they are aliens, then they must kill her, but in a way that isn't possible for her to predict.

Dick has bought a new camera, with which he makes Mary angry, by constantly taking her picture against her wishes. As a result, Mary decides that the two need some time apart. Meanwhile, Sally's coat is ruined when Harry wears it out in the rain, but he claims that the Channel 10 weatherman said it was going to be sunny. Sally marches down to the station and tries to convince them to pay for her coat, but it soon becomes apparent that Sally is excellent at predicting the weather, so they give her the position. Dick, however, is worried that Sally's spot on prediction of the weather will attract unwanted attention and so, when she discovers that Rutherford is to be hit by tornados, he orders her to report otherwise.

Mary's mother Martha arrives in town and Dick decides to tell her what Mary really thinks of her - that she ruined her childhood. Angry, Martha tries to attack Dick and falls over, ending up in hospital. When Dick goes to visit, however, Martha tells him her side of the story, and a deeply moved Dick takes her side and promises to tend to her during her recovery. Meanwhile, Harry and Sally get a nasty surprise when throwing junk in the time space portal - a new alien.

After hearing a pitch for a timeshare, Dick is sold and, unable to afford it entirely, he convinces Don to pay the other half. When Dick, Mary, Sally and Don take their first holiday there, however, they find it to be dismal; small and windowless, with nothing in the surrounding area but a prison. Meanwhile, Tommy has finally outgrown Harry, leading Harry, paranoid that he is shrinking, to consult a doctor.

Dick accompanies Mary and Nina to a book-signing for a self-help book entitled 'A Road Map to Happiness', and despite first thinking it stupid, Dick opens the book and is immediately converted. He then concludes that his relationship with Mary stands in the way of his happiness, and attempts to break up with her. At college, Tommy is attempting to get into a fraternity but is doubtful that he'll pass the entry rituals, so he enlists Sally's help, but she just ends up making it harder. Meanwhile, Mrs. Dubcek gives Harry the job of painting the kitchen ceiling, and he is determined to create a work of art.

Dick discovers that Mary has been receiving elaborate love letters from a mystery man named 'Scoochie' and confronts her about it. She reveals that she has been receiving them for years but has no idea who Scoochie actually is, so Dick pretends that it has been him all along. This goes wrong, however, when the real Scoochie arranges to meet Mary at the Medieval Festival. Meanwhile, after another alien unit operating in Ohio wins an award over the Solomons at the Alien Award Show, Sally and Harry make it their mission to track them down, and eventually move in with an Amish family, who they believe to be the other unit, since they are so different.

With the identity of Scoochie revealed to be Liam Neesam, who had visited Pendelton three years ago, Dick is panicked, and follows Liam and Mary to dinner, where he overhears Liam offering her a job with a six-figure salary. The other Solomons suggest that Dick reveal himself as another alien in order to gain Liam's respect. When he does, however, Liam reveals that he doesn't care for Mary, but that she is part of a huge plan to transform the Earth's entire population into monkeys, and rename it Planet Monkey World, so that it may be an exhibit for aliens. Meanwhile, Sally, Harry and Tommy discover that their favorite movie, Arthur 2: On the Rocks' has a 'prequel' - Arthur.

Mary is having trouble dealing with what she has just seen - Dick transforming Liam into a monkey, which he had done to stop him doing the same to the Earth's population. Dick consults the other Solomons and they decide that the best approach is to deny everything. Meanwhile, Mary meets with Nina and Judith, who confess that they believe Dick to be an international terrorist, so when Dick and Mary next meet, she demands that he tell her the truth about himself. So, Dick tells Mary that he and the others are aliens. Mary's reaction is first disbelief, then shock, and then she finds it sexy to be dating a spaceman. Elsewhere, the local store has been robbed and Sally catches Don hiding in the frozen foods freezer, where he admits that he hid because he was scared. Harry takes a different line and asks the shopkeeper Sam out on a date, but later runs into her working at a posh restaurant, where she instructs him to call her Samantha. Confused, Harry believes that he is dating twins.

The Solomons are struggling to take in the news - they have been ordered back home due to Dick's transgression with Liam. Dick's first instinct is to ask Mary to come, so he takes her to the planetarium before breaking the news to her that they are leaving, and asking her if she will join them. Meanwhile, since admitting his fear to Sally, Don has decided to quit the police force and open a muffin store, but Sally is disgusted by this career choice and decides to whip Don into shape - and turn him into a hardy police officer. At home, Harry and Tommy are attempting to organize a farewell party for the aliens, but have no money, so they decide to max out their credit cards and not worry about paying the bill, since they'll be halfway across the galaxy - they even hire Elvis Costello to sing Fly Me to the Moon.