Continuing from "Ricksy Business", Rick, Morty and Summer spend six months repairing the house and screwing around with time frozen. After unfreezing it, the trio ends up in a decaying dimension. They split into separate timelines whenever they are uncertain about something. Rick becomes paranoid, thinking that his duplicates want to kill him, but eventually he calms down. A creature in charge of safeguarding time appears and gives them collars that integrate all the timelines, then attempts to arrest them because Rick stole the time-freezing crystal. Rick, Morty, and Summer show uncertainty on purpose and break the collars, splitting into sixty-four timelines, and they simultaneously beat up the same creature. Rick then repairs the collars, and they successfully integrate all the timelines. In one timeline, Rick attempts to sacrifice himself and let Morty live by giving him his collar, but ultimately he survives too. Meanwhile, Beth and Jerry hit a deer, and bring it to an animal hospital. A hunter claims the deer for his own because he shot it before the accident. Beth is able to save the deer's life and release it.

Rick takes Morty on a trip to teach him how to pilot the flying car. When Rick realizes that Jerry has followed them without being noticed in the back seat, he leaves him in a daycare specifically designed for Jerries from alternate realities. Jerry socializes with other Jerries, some of them left there indefinitely because their Rick and Morty never returned. Rick sells an antimatter gun to Krombopulos Michael, an alien assassin who intends to use it to eliminate a gaseous being whom Rick nicknames Fart that is held captive by alien authorities. Rick plans to spend the day at the "Blips & Chitz" video arcade, but Morty decides to stop the assassin. After Rick and Morty release Fart, they are chased by the authorities. Fart uses telepathic powers to kill the authorities, which also leads to civilian casualties. Later, Morty learns that Fart wants to eliminate all carbon-based life forms. Morty then kills Fart using Krombopulous Michael's antimatter gun. Rick and Morty return to pick up their Jerry, but it is left unclear whether they got the right one.^{[lower-alpha 1]}

Rick attempts to loot a damaged spaceship with Morty and Summer. They find Unity, a hive mind and Rick's ex-lover. It plans to eventually assimilate the whole universe. Beta 7 is a male hive mind who has a crush on Unity, which it rejects. In a planet completely assimilated by Unity, it and Rick have parties, have sex, and drink and use drugs together. In light of all the revelry, it loses control and the planet is left messy and untended. Summer finds the assimilation unethical, until she and Morty witness some inhabitants regain their identities and start a race war. Eventually, Unity decides to leave Rick for its own good. Meanwhile, Beth and Jerry find a secret underground room with a slug-like monster. The couple has an argument where Jerry makes accusations against Rick and Beth tries to defend her father. The monster breaks free of its chains and accuses Beth and Jerry of having the worst relationship it has ever seen. An upset Beth confronts a visibly distressed Rick, who attempts suicide in the garage but fails.

Alien parasites plant fake memories in the minds of the Smith family and pretend they are friends and family members. Every time the family reminisces about the past, the aliens reproduce. The family can't distinguish real people from aliens, so eventually they can't even trust each other. To prevent further spread, Rick locks down the house. At first, the only alien present is the fake "Uncle Steve"; they are soon joined by other aliens including Cousin Nicky, Sleepy Gary (who poses as Beth's husband and Jerry's lover), the family butler Mr. Beauregard, Frankenstein's Monster, a talking pencil named Pencilvester, Tinkles the Fairy Lamb, etc. Mr. Poopybutthole is an unusual yellow creature who did not appear in any previous episode but appears to be a longtime friend. Eventually, Morty discovers that the parasites can only create positive memories, allowing the Smith family to confirm one another's existence and kill all the aliens. As they sit down to dinner, Beth shoots Mr. Poopybutthole, thinking he is a parasite as well, but he turns out to be real.

Post-credits scene: Mr. Poopybutthole goes through physical therapy. Beth is devastated.

A massive alien head (a "Cromulon") appears over Earth, demanding to hear an original song, so Rick and Morty improvise "Get Schwifty". The whole planet is abducted and forced to participate in a musical talent show, where the losers' planets are obliterated via plasma ray. Morty steals Rick's portal gun and leaves him alone with Ice-T—the only musician to survive an earthquake that struck the Grammy Awards—to make a hit original song and save earth. Morty stumbles across Birdperson (living with Tammy since "Ricksy Business"), who persuades him to go back to Rick. Ice-T is revealed to be an ice alien who does not initially care about Earth, but he later changes his mind and saves the planet. Rick, Morty, and the US president win the competition by improvising "Head Bent Over". Meanwhile, Jerry, Beth, and Summer enter a religious cult based on an incorrect interpretation of the message from Cromulons. The movement quickly disbands after realizing it was all a musical talent show.

Rick's flying car will not start, so he and Morty investigate the problem. The car's battery contains a miniature universe and Rick has been threatening their destruction if they do not generate electricity. Inside it, Zeep Xanflorp, that universe's top scientist, created a second miniature universe for the same purpose. Rick, Morty and Zeep are left stranded in a third miniature universe, as the pilot commits suicide and destroys his ship. Rick and Zeep constantly fight, and Morty abandons them and becomes a native chief. Morty forces the two scientists to work together to escape. While escaping, Rick reveals that Morty can turn into a car if needed. Ultimately, Rick and Morty leave the battery, trapping Zeep. Zeep is forced to discontinue his miniature universe research and have his people resume generating electricity to prevent Rick from destroying their universe. Meanwhile, Summer is forced to stay in the flying car, which uses violence to "keep Summer safe" from strangers, while she protests. However, it is effectively pardoned once it prepares a peace treaty, ending the human-spider war that has existed in this alternate reality. As a result, ice cream is now served with flies to appeal to spiders.

Rick becomes "Tiny Rick" by transferring his mind to a teenage clone of himself in order to kill a vampire in Morty and Summer's school. Tiny Rick is outgoing and popular, but subconsciously cries for help in song lyrics and drawings. Much to the disdain of her classmates, Summer deliberately gets him expelled by denouncing him as the killer of the vampire Coach Feratu (a reference to Nosferatu). Morty and Summer eventually persuade Rick to return to his body. Meanwhile, Jerry and Beth experience couple therapy on an alien planet. Two manifestations of the partners' perceptions of one another are created: Jerry's Beth is embodied as a towering, hostile Xenomorph-like insectoid, and Beth's Jerry is a servile worm. The insectoid Beth goes on a rampage with the help of the worm Jerry, killing several couples and employees. Eventually, Jerry acts in a brave way, causing Beth to envision a strong Jerry, which in turn envisions a goddess-like Beth, who destroys the insectoid monster.

Jerry is treated in an alien hospital after unknowingly ingesting some bacteria stored by Rick in a pint of Cherry Garcia. While his family is in the waiting room, watching an assortment of TV channels from alternate realities, Jerry is asked by doctors to donate his penis, to be converted into a replacement heart to save the life of civil rights activist Shrimply Pibbles. Jerry complies, but publicly tries to talk his way out of it nonetheless. This causes Jerry to be hated by the public, but also raises awareness as well as money to buy a synthetic heart for Pibbles. Eventually, Jerry changes his mind and holds the doctors hostage, demanding that they go through with the transplant procedure, but Security stops him. The family is then sent home, with Beth chastising Jerry that he should not care so much about what strangers think of him.

Rick and Morty visit another planet to purchase wiper fluid and witness "The Festival", an annual event where the local populace commits crimes for one night without consequence. After initial hesitation, Morty forces Rick to rescue Arthricia, a young alien girl, who proceeds to betray them, stealing Rick's gun and spaceship. Rick calls Summer, who transports them advanced armor suits. Morty then goes on a seemingly uncharacteristic killing spree before Rick knocks him out, and he and Arthricia—who desired to stop the Festival—storm the castle of the corrupt nobility who introduced it, slaughtering them. The planet's remaining inhabitants decide to create a new society; however, rioting breaks out over disputes, and one suggests keeping the Festival after all. Morty feels guilt over his rampage, but Rick (falsely) blames it on the effects of a candy bar he ate, and asserts that his character remains unchanged.

Rick and his family attend the wedding of Birdperson and Tammy, whose guest list includes seventeen of the Federation's most wanted — including Rick and Birdperson. At the wedding reception, Tammy reveals herself to be a Federation agent and kills Birdperson. Numerous agents invade the building, starting a battle against the guests. Rick gets his family out of the wedding safely, but they are unable to return home as the Federation would be looking for them there, so Rick takes them to a terraformed asteroid. Rick overhears Jerry proposing to turn Rick in and return to Earth, so Rick allows himself to be arrested. His family returns to Earth, which has joined the Federation and is crowded by alien tourists. Jerry is assigned a job by the Federation.