Brown visits Merla’s classroom and sees his former bass on the wall. He reminisces about his performance on the stage of last year’s summer festival with his roommates in Collateral Damage (the band name) and wants to do it again. Merla suggests getting the band back together, so he borrows the bass again and does so.
Meanwhile, Karen is released from the holding cells off her charge of aggravated assault against an officer after a year of doing time. Charlie sternly warns her not to try anything, promising she will not get away with it this time. Of course, Karen disregards him, immediately seeking vengeance against Brown for getting her arrested in the first place. She recruits and manipulates a professor, Sean Kerosol, to help her act out her ploy.
Karen later conspires with Sean concerning more details of her plan. Claude (guard) overhears this, however, and confronts Karen about her suspicious activity. She lies through her teeth and tells him Sean is preparing to stage a private party in the gardens, despite ERA protocol mandating staff must disclose all details of upcoming or proposed public events to Security and Administration.
Fact-checking with Sean in the gardens, Claude uses his immature clone, Cloo, via Electi ability who tricks Sean into spilling crucial information to him to relay to Claude, who intercepts and catches Sean with the discrepancies with Karen’s testimony. Sean is forced to make the event official, and thanks to Claude’s interrogation is also forced to disclose new details to him, such as making the event a public battle of the bands, and giving out an $8000 cash prize to the winning contestants from his own wallet.
Sean visits Hugo, a former CD band member, separately planting the idea to reunite the band. This way, while the band performs, she will be able to “punish” Brown while he’s distracted and have her revenge.
Brown, Saki and Hugo seek out a new drummer, after hearing the former two’s roommate Xander has gone AWOL and/or graduated. Brown finds Kai, a friend from an unrelated traumatic experience involving a kidnapping-turned-ping pong tournament. Kai agrees to fill in for drums, and offers to set up their borrowed equipment in the abandoned building.
Meanwhile, Karen enters herself as a bassist to compete against Brown. This way, she can sabotage and humiliate Brown throughout the event, rigging each round so that the longer they stay in, the worse her revenge is enacted. She searches for band members gullible enough to join her and dumb enough to not raise suspicion of her ulterior motives, finding keyboardist Casti having recently quit another band and Cassie, learning to play drums. Together, they form the Offchords.
Skyber hears of Brown’s plan to reunite CD and uses this as an opportunity to gain more traction at her underground casino. She singles him out and offers to be the band’s sponsor, on the condition of Brown entering and winning Sean’s Rock-a-Thon event. Brown feels he has no choice but to accept, given he is already an employee in her casino. Cloo, untethered from Claude’s watch, stumbles into the Offchords’ rehearsal session and asks to join as guitarist. At first, Karen thinks this is another ruse by Claude, only to find that Cloo really isn’t Claude, and has the mind of a child, thus especially susceptible to manipulation.
Claude discloses his findings and his clone’s whereabouts to his colleague, Charlie, an experienced officer. Untrusting of Karen from last year’s aggressions, he advises Claude to spy on her vicariously through Cloo. Meanwhile, he alerts his squadron of fellow officers Joan and Oliver to help keep eyes on the event and its participants for any suspicious activity.
Sean is appointed to judge the concert, along with fellow professors Phoenix Mara and Seanen Goldman who will also act as project supervisors. They bond over their taste in music and help Sean design and build the stage for the concert. Sean feels the first sense of guilt over this.
The week before the event starts, Collateral Damage rehearse their new songs in their boys-only club room, carved out of an empty room in the abandoned building. However, one night Kay (a woman) crashes their rehearsal, and Kai almost shoos her out before the rest of the band vouches for her validity as “one of the boys”. She is allowed to stay, and is eventually offered the role of sound producer and roadie.
Round 1 goes off without a hitch for OC, but before CD can go on Karen calls ERA Security anonymously to report Saki’s illegal drug possession, getting him arrested and unable to play. Minutes before stage, Skyber deploys Nova and makes the band accept them as their new lead guitarist. They win the prelims. So do the Offchords.
Before Round 2, Karen sneaks backstage and tampers with the sound equipment, maxing their volumes. CD, unaware, instantly blows out (and blows up) the stage speakers. Brown temporarily solves this by hooking everything up to their one still-working amp, while Kay gathers the spare speakers, mics, and amps for them to finish their song. They tie against the round’s opposing band, but Sean rigs the votes and declares CD the winners on the grounds of having a good sound producer. This decision is only made just so Karen can exact more punishment onto Brown later on.
Meanwhile, OC is getting slightly wary of Karen, but nevertheless ends up bonding more and more as the event progresses. Clyde sets up a mini Halloween costume contest on Sean’s stage in between rounds, wherein the prize money gets stolen. No surprise there.
Skyber confronts Sean and Karen independently, suspicious of their true motives. Karen is unphased, but when Sean comes to her later wracked with guilt, she blackmails him to stick with the plan, or she’ll expose everything he’s done for her.
On Round 3, Sean is forced to meet CD backstage and offer an apology gift for the speakers, giving them a bottle each of cola. Brown is given a special one. When they get on stage and play their song, Karen waits for a minor distraction via Brown messing up his lyrics to drop loose metal beams and other debris from atop the stage. This backfires as Brown’s drugged cola takes effect, making him stumble out of the way just in time. Skyber notices this, and tells Pearl to tell Charlie and Phoenix (who are already aware of what’s going on) to go backstage to intercept whatever is causing this. Phoenix almost discovers Karen, until she knocks him out and gets away before he could see her face. Charlie calls in Joan and Oliver, who evacuate the audience and postpone the concert. He and Skyber confront Sean who confesses almost instantly due to his predisposed guilt, discovering Karen was the one behind the sabotage, and that Sean himself drugged Brown. Sean is arrested.
Goldman spends the entire time treating Brown’s drug overdose and Phoenix’s heavy injuries. As Sean is no longer a qualified judge, Goldman declares CD winners of Round 3. Brown wakes up in the medical ward, and once he makes a significant recovery, Skyber visits him to apologize for forcing her sponsorship on him. Brown is hesitant to accept, but Skyber offers sanctuary for the band (including Hugo, who had not yet been briefed of its existence) under her casino until the final round, where she will ensure their security.
Charlie and Claude meet to gather evidence against Karen before the fourth and final round. They discover her recent criminal activity through her recent on-campus purchases of screwdrivers and lethal doses of drugs, and search through her government files. Charlie pulls some strings throughout the Department outside his jurisdiction for DNA confirmation via forensic examination of tampered items around the stage; Claude switches himself out with Cloo and gathers info about Karen’s true motives against Brown. He manages to get Cassie and Casti on his side, making them lose their trust in Karen. However, he does not notice Karen stealing a pocket knife from Casti.
Finally, the day of the final round, OC goes on first against a missing CD, where Karen’s band members reluctantly play. Claude is disguised as Cloo, the guards lock down everything, and CD’s non-band friends are advised to stay away entirely. Everyone is on high alert, waiting for Karen to make a move. Karen remains docile, though her band decides to switch the song on her last-minute, humiliating her and causing her to make several mistakes. Finally, she lashes out on them on stage. Cassie, enraged and betrayed, bashes a microphone stand over her head. CD is still nowhere to be found. Karen grows unstable. Finally, CD goes on and their superior performance triggers Karen’s last ditch effort at sabotage, this time a Hail Mary attempt to straight up murder Brown with Casti’s knife. Cassie runs away. Kay, just in time, jumps in front of him and takes a stab to the gut for him, incapacitating her. This causes a chain reaction of almost everyone involved to take Karen down. Claude confiscates the knife and Charlie shoots her rope arms off, upholding his promise of justice. Skyber helps evacuate the bands and Nova calls for medical attention. The rest of the guards secure and evacuate all civilians. Karen is arrested and permanently released from ERA on a stretcher to the federal penitentiary.
Days later, Administration struggles to play cleanup. They scrub all records of the event from their data centers, erase the story from the news, and announce to the students to not raise alarm, lest the school may face termination. They send a letter to Charlie, ordering him to release Sean from prison to resume teaching to save face, collecting the $8K as post bail. Charlie refuses, instead going to Goldman to take the money and personally redistribute it to all eight surviving victims of the final bands, CD and OC. Brown, Nova, Kai, Hugo, Kay, Cassie, Casti, and Cloo all each get $1000 in cash winnings, and Sean remains in prison. To celebrate, CD plays a final impromptu rooftop concert, with Saki returning to play with them.