After Donna, Gordon, Joe and Cameron get to COMDEX, they manage to rouse interest in the Giant, only to have the rug completely pulled out from under them with Whitmarsh, Donna's former TI supervisor, announcing the "Slingshot", a clone of the Giant which will be cheaper and easier to sell. As a result, Gordon and Donna have a complete blowout in the hotel room, and he has to strip out the extras that made the Giant unique. Cameron nearly has a Heroic BSoD over the fact that the Giant is now simply another MS-DOS clone that can be $100 cheaper than the Slingshot. Joe is forced to agree with Gordon in the interest of salvaging something.
Gordon and Donna get car-jacked, and then Joe decides to burn the first shipment of Giant computers.
After Gordon's Sonaris program accidentally wipes the Mutiny BBS software, Cameron nearly has a complete meltdown.
Gordon desperately tries to seek a human connection after finding out that he has brain damage. When Gordon takes his daughters to their maternal grandparents' house, Gordon tries to seek a connection with his mother-in-law Susan only to find that she wanted him to pay her and Gary back for the failed Symphonic project.
Gordon and his brother Henry have a falling out over the former having an affair with the latter's ex-girlfriend. The incident scars Joanie and Haley so much that the former wants to keep quiet about it so her parents don't fight.
When Joe comes to Mutiny to discuss Westgroup's new network rental terms, Donna has an emotional meltdown. The situation gets worse when Joe pulls the plug on Mutiny.
Lev gets beaten up by a group of people who pretended to be the guy he was interested in.
Tom's revelation that he grew up in poverty, and his mother had just been laid off from her job as a paramedic before showing up to lunch with Cameron, but wore her uniform anyway.
Gordon's deteriorating mental condition leads him to see conspiracies that aren't there and believe that Donna is turning against him.
Gordon loses track of his car in a parking garage and ends up injuring his ankle in a little-used stairwell. Since cell phones were a luxury item in the mid 1980's, Gordon has to struggle up the stairs to get someone's attention. After being loaded on a gurney, Gordon has an emotional breakdown when he finally finds his car as the paramedics take him to the hospital.
Donna finds out about Gordon's affair, and it nearly precipitates a divorce. Their daughter Joanie does not take the outing of that secret well either.
Joe getting to the lawyer's office to find Sara has already signed the divorce papers.
Gordon's Sanity Slippage is increasing. He has a notebook filled with dates and times of incidents such as sudden vision changes. It's clear that his problems are exacerbated by having to deal with Joe, as well.
Cameron is slowly realizing that Mutiny as she conceived it is slipping away. She'll always be the co-owner with Donna, but she now has to "play well with others" instead of going it alone. What makes the whole thing worse is that Donna and Cameron have become trapped in a vicious cycle where Donna reacts to Cameron's Control Freak tendencies by doing things behind her back, and Cameron reacts to this by becoming even more of a control freak, causing Donna to go behind Cameron's back again, ad nauseum.
In "Yerba Buena":
Cameron tries to go home to claim her father's old motorcycle, but suffers so much anxiety at the prospect of seeing her mother and stepfather again that the bike gets sold, she and Bos have a fight, and she ends up disappearing for a week and nearly blowing things up with Donna. And then, during her efforts to make amends for her disappearance, she finds out that Donna lied to her about Diane vetoing her attempts to fire the SwapMeet guys. By the end of the episode, she's huddled up in a fetal position.
Before his argument with Cameron, Bosworth has a falling out with his son James. Because James had to work during the holiday weekend, Bos builds his grandson's crib, and James accuses his father of trying to be a family man to try and make up years of paternal neglect.
In "And She Was", Donna and Cameron have a heart-to-heart on the grass, wherein Donna admits that she lied to Cameron and manipulated her, and apologizes for it, and Cameron forgives her. It could have been a Heartwarming Moment... except then it's revealed that this is all a drug-induced hallucination. And then she returns home and discovers that Cameron is so hurt by her actions that she's moved out of their house while Donna was away.
In "The Threshold":
After Cameron and Donna try to mend fences, with Donna even throwing a party at the Mutiny offices to celebrate Cameron's marriage to Tom, Gordon pulls Cameron aside to tell her that Donna still wants to go ahead with the IPO, which Cameron misinterprets as a warning that Donna's going behind her back again, and thus she reacts by calling together the majority shareholders and demanding a vote on the IPO. She and Donna each threaten to quit if their side loses, and the shareholders reluctantly back Donna. The look of betrayal on Cameron's face as she watches the people she trusts express their lack of confidence in her leadership is heartbreaking.
Related to this is the clear conflict Bosworth shows as he reluctantly votes with the others against his surrogate daughter.
In "You Are Not Safe":
Mutiny finally goes public, but it's a mess; Donna struggles her way through the presentations and is very clearly uncomfortable doing interviews, Bosworth is still clearly sore about Cameron's ouster, and the stock opens about 60% lower than Diane expected. As they watch the stock value drop, Donna appears to be on the verge of a nervous breakdown.
Ryan, who's been missing for a while, finally turns up at Joe's place. At first, it seems like they're going to have a heartwarming reunion, until Joe explains that Ryan's only two options after violating the CFAA are to either disappear or admit to his crimes and face a year in jail... after which he will be banned from working in the computer industry for five years, and forbidden from working with Joe ever again. He tells Ryan to sleep on it. Ryan instead publishes a manifesto confessing to his crimes and then jumps off of Joe's balcony, killing himself.
Cameron and Donna seem to be on the verge of reconciling, when Donna incautiously suggests dumping Joe if Cameron doesn't want to work with him. An argument breaks out between them as Cameron points out Donna failed her Secret Test of Character, and Donna leaves to cry in her car.
Gordon's heavy metal exposure causing cognitive problems in the 1980s seems to have advanced to also affecting his bones or muscles, occasionally rendering him unable to easily move up a flight of stairs.
Heartbroken after Cameron got her kicked off of the browser project at the end of season 3, Donna has transformed into a ruthless venture capitalist.
Cameron told Tom about her one-night stand with Joe, and in order to save their marriage, agreed to return to Japan to work remotely on the browser. Unfortunately, Tom ended up leaving her anyway after she proved unable to conceive a child, and she lost her enthusiasm for the project, instead trying to develop a new game. But even that ends up making her miserable, as the video game market is no longer made up almost entirely of geeks like her, and thus she finds herself subjected to focus groups populated by the kind of people she disdains.
Gordon and Joe's plans to rush out a browser were hindered by Cameron's return to Japan, and Gordon instead developed an Internet Service Provider while Joe kept waiting for Cameron's prototype browser to arrive. The ISP was actually successful, but then America Online came along. By the end of the season premiere, Gordon watches as his company collapses.
In "Miscellaneous", Cameron is tired of Atari refusing to release her game and decides to have a copy leaked to Electronic Gaming Monthly, figuring they'll be able to help pressure the company into releasing it. To her shock, the review derides the game as a complete mess and Cameron cries to Joe on how the project she devoted so much time to has become a disaster.
In "Tanya and Nancy", Bos becomes desperate to save the Rover project and manipulates Cameron into writing a crucial algorithm for him. The fallout is bad; while it helps Rover get funding, Cameron resents that Bos used her, Donna is livid when she finds out that Bos gave Cameron information about Rover, and Joe is pissed that Comet now has to face off against a well-funded competitor.
In "Nowhere Man", Bos suffers a heart attack, and Cameron thinks that she caused it by refusing to help file the patent for her algorithm, and Donna, who was actually responsible, cheerfully encourages this belief because she doesn't want Diane to find out about the role that she played in Bos' heart attack.
In "A Connection is Made", Donna's attempt to preserve her control over the Rover project blows up in her face as Diane kicks her off of the project, and she turns to alcohol to compensate, which leads to her making a terrible ass of herself in front of Joanie, and culminates in her getting pulled over for drunk driving and forced to call Gordon to bail her out. As she tries to preserve some semblance of pride by boasting that her younger self couldn't handle her current self, Gordon sadly tells her that deep down, she's still the same person she was back then... and he loves that person. Donna breaks down crying.
In "Who Needs a Guy", a broken air-conditioner at the Comet offices spurs Gordon into one of his finest days in recent memory. Stimulated by the challenge of trying to repair the damn thing, he makes peace with Haley and convinces her to come back to work, comes up with a plan for revitalizing Comet in the face of Rover's powerful new algorithm, and actually fixes the AC. Feeling on top of the world, he resolves to celebrate by going home for a night in with Katie... and then he starts suffering another one of his episodes, this time in the form of a vivid hallucination, imagining as he walks through his house that he's going back in time, first to when he and Donna were still married, then back to when they and Joanie and Haley were all still living in Texas, and then back to when Haley was a baby. And then he dies.
"Goodwill" has most of the main characters gathering at Gordon's house to clean it out, and naturally, it's depressing as hell.
Donna finds herself forced back into the role of Team Mom, forced to keep everyone else together while she's still wrestling with her own grief.
Cameron has to deal with both the loss of one of her few remaining friends and her dread that her relationship with Joe will fall apart.
Joanie is revealed to have completely blown off her college applications, convinced that she would never get in anywhere.
Joe and Haley launch a caper to recover one of Gordon's sweaters from goodwill after Joe accidentally donated it, as Haley had hoped to keep it. They are unsuccessful, but Haley makes her peace with the loss of the sweater. Joe, on the other hand, spends the rest of the episode deeply depressed.
Katie shows up briefly, and we discover that she's so heartbroken that she has quit Comet and now intends to move to Seattle.
Joanie has reached the point where she can't stand to be around Donna anymore, and thus leaves for Thailand.
In the wake of Gordon's death, Joe ejected Haley from Comet and completely redesigned the site in accordance with the vision that he and Gordon came up with in "Who Needs a Guy". Haley is understandably pissed about this and decided that she wants nothing more to do with Joe, forcing him to reach out to Cameron to help with redesigning the site. Secondary to this, Haley finally works up the nerve to ask her crush out, and is rejected.
The strain of actually working together again completely destroys Joe and Cameron's burgeoning relationship, particularly after Joe gives Cameron the nearly-impossible task of optimizing Comet for Netscape, which hasn't even officially come out yet. She manages to get an advance copy of Netscape to toy around with, only to discover that Netscape has already partnered with Yahoo!, effectively leaving Comet obsolete.
With her relationship with Joe having fallen apart, Cameron's partnership with Alexa soon follows, as she realizes that Alexa's only real talent is in schmoozing.