Four years have passed since Mutiny’s failed IPO and Ryan's suicide. Mutiny has folded, Donna and Gordon have divorced, Gordon has completed work on the NSFNET regional network Joe and Ryan had started, and Donna is now a senior partner at Diane’s venture capital firm. Donna contacts Joe, who is now an independent consultant, stating that she has a proposition for Cameron; however, he refuses to be her middleman. Cameron, now working for Atari, goes to Las Vegas for COMDEX to promote her latest game, Space Bike IV; Joe shows up at her booth, and the two reconnect. At home, Gordon has trouble dealing with Joanie's rebellious behavior as he tries to entertain his new girlfriend. Joe and Cameron attend a suite party hosted by Atari, and Cameron finds Donna there. Donna tries to pitch her project and wants to make amends, but Cameron, who is still resentful towards Donna, refuses to hear her out. Joe goes to check on Cameron,-- in her suite. Before Cameron leaves Las Vegas, she reconsiders Donna's proposal, and when Joe returns to San Francisco, he finds a memo faxed to him by Donna about the project, the World Wide Web.
In the three years since their meeting over the World Wide Web, Joe and Gordon have formed a new internet service provider called CalNect in the former Mutiny offices. Joe expresses his frustration over Cameron’s inability to get their web browser, Loadstar, completed; Gordon shows him Mosaic, a new browser gaining in popularity, and he implores Joe to abandon the web browser project to help him run their company. While doing a focus group of her new game Pilgrim, Cameron expresses frustration as the testers show disinterest towards the game. For his 40th birthday, Gordon has a lavish backyard party featuring a performance by Blue Man Group. At the party, Diane tells Bosworth that CalNect would face stiff competition from America Online if they expand west. After Cameron gives Joe the final version of Loadstar, he gets a new idea, a way to index every website on the Internet. At her venture capital firm, AGGE, Donna meets with a startup company called Rover, and she gives them funding after they propose to use their algorithm originally designed for cataloging medical databases to index websites and make them searchable. Cameron tells Joe that Tom had left her and that she’s not returning to Japan.
Cameron begins working on a new game for Alexa, which precludes any quality time with Joe. Bosworth and Diane get married at Palo Alto City Hall. While discussing her recent issues with Gordon, Donna tells him that Rover is outperforming Comet in terms of web traffic; however, she believes that keeping users around is the key to winning the browser wars. Gordon decides to use Donna’s comments as a basis to improve Comet by transforming it into a web portal; however, Joe refuses to hear advice from their biggest rival. Diane reveals to Donna that she plans to retire as a managing partner at AGGEK. Gordon admits to Joe that he was right about Haley, and Gordon allows her to return to work at Comet. Despite agreeing to help Gordon redesign Comet, Joe confronts Donna, accusing her of trying to sabotage Comet, but he later apologizes after she lashes out at him for being unfairly demonized. As Gordon prepares for a date with Katie, he has hallucinations from the past. When Donna calls Gordon, Katie answers the phone and reveals that Gordon had died. After Gordon’s death, Joe and Cameron face uncertainty with Comet’s future.
Faced with mounting pressure from both AOL and MCI, Gordon decides to sell CalNect. Joe sees Haley’s work, and he wants to buy Haley’s Comet to develop it further; however, Haley refuses to sell, insisting that she wants to work on it herself. Joe and Gordon argue over letting Haley develop the website, which Joe renames as simply "Comet", with Gordon noting Joe’s history of pushing people beyond their limits. Gordon allows Haley to continue working on Comet with the stipulation that she walk away the moment she is no longer having fun with the project. Atari discovers that Pilgirm was leaked to Electronic Gaming Monthly, who gave the game a scathing review, and Cameron claims responsibility for the leak. At AGGEK, Donna is displeased with Rover’s progress. Diane reprimands Donna for her hostility towards Trip as well as for being too harsh towards the Rover team; Donna invites the Rover team to her house for a dinner party in hopes of easing tensions. Trip later informs the other partners about Comet competing against Rover; while having dinner with Gordon, Donna learns that he and Haley are competing against her.
List of Halt and Catch Fire episodes
Donna fires Cecil from Rover so she can have an outside programmer reverse engineer Cameron’s algorithm. As Gordon, Joe, Cameron, and Katie celebrate Haley’s birthday, Cameron tells Gordon that she wants to get out of tech. Haley later sends Cameron a link to a fansite dedicated to her work, and it renews her confidence. Cameron later meets with Alexa Vonn, who offers Cameron financial assistance for a new project. Donna informs Gordon that Haley is failing two classes. He tells Haley to take time off from working on Comet to focus on her school work; however, she refuses. After taking Haley to a local fast food joint and noticing the interactions between her and a female employee, Joe believes that Haley isn’t like other teenagers and insists that she needs Comet, but Gordon does not agree with him. Bosworth finally admits to Diane his bad real estate investment and that Cameron helped him with Rover's search algorithm. Diane then orders Donna to buy Cameron’s source code outright and turn control of Rover over to Trip. Cameron agrees to sign over the algorithm to Rover, but she turns down payment. Cameron senses that Donna is in disarray, but Donna leaves before she can figure out why.
Joe and Cameron reconcile over the events, both professional and personal, of the past three years. Donna sets up an incubator for Rover, and she appoints her assistant Tanya Reese to oversee it. Gordon finds out that his younger daughter Haley had skipped school; as he brings her to the office, CalNect is facing a crisis over bandwidth due to their new flat monthly rate as a response to AOL's threat of expansion. Gordon then tasks Haley with indexing Joe’s research, and she creates her own website, "Haley's Comet". At AGGE, Donna complains to Diane about a new senior partner, Trip Kisker, being brought on to the firm. Atari informs Cameron that they have decided to shelve Pilgrim indefinitely. As customer service calls increase at CalNect, Gordon tells his employees to contact their backbone provider MCI to try and increase their bandwidth capacity; however, he realizes that MCI is starting their own ISP when they refuse Gordon's request. Bosworth reveals to Gordon that a bad real estate investment had wiped out his savings. At AGGEK, one of the partners suggest they should put web business investment on hold; however, Donna convinces them to keep Rover. After the other partners insist on an outside consultant to oversee Rover, Donna brings on Bosworth to manage the incubator, much to Tanya's disappointment.
At Comet, Joe and Gordon review Rover, and both agree that the website is substandard. Cameron tells Joe that Comet needs a more sophisticated algorithm to index websites as the World Wide Web continues to grow to possibly millions of websites. At AGGEK, Tanya and Bosworth argue with Donna over launching Rover too early in response to Comet. To assist in indexing, Joe and Gordon hire Dr. Katie Herman as chief ontologist for Comet. The Rover team requests Series A fundingto better compete with Comet, but Donna is hesitant. After rejecting a low-ball buyout offer from AOL, Joe and Gordon meet with a venture capital firm to expand Comet; however, they ultimately decide against pursuing VC funding. Cameron buys a plot of land and a used Airstream trailer; after Cameron has trouble with the trailer’s plumbing, Bosworth comes by to help her fix it. Bosworth reveals to Cameron his personal debt and problems at Rover, and Cameron helps him out with Rover’s algorithm. Donna eventually gives Rover Series A financing; however, she becomes suspicious of the origin of their new indexing algorithm.
Donna questions Cecil, Rover's lead programmer, over the new search algorithm. Gordon and Katie start a relationship. At Comet, Joe worries about Rover’s newfound funding. Donna freezes additional hires for engineers at Rover until Cecil can provide specifications for the algorithm for legal purposes. Tom comes by Cameron’s trailer unexpectedly to give her their divorce papers, and the two reach closure with their failed relationship. Bosworth tries to get the specifications from Cameron, but she refuses to help him further, as it would put her in conflict with Joe. While having dinner with Donna, she questions Bosworth over the algorithm, and he suffers a heart attack. When Cameron comes to the hospital to check on Bosworth, Donna realizes that she wrote the algorithm, and she tells Cameron to stay out of her life. Cameron later admits to Joe that she indeed helped Bosworth. Gordon reveals to Donna that Bosworth is $300,000 in debt, which is why he turned to Cameron for help.