This year, Dwight decides he'll really get into the spirit of Halloween. He's got the perfect costume: a real jack-o'-lantern worn as a mask. He walks around the office scaring co-workers. It's great fun until it's not. He's trapped himself in the pumpkin, unable to safely slip it off his head. We see a montage of Dwight and Jim trying to figure out a way to stab or bludgeon the pumpkin off, but all the attempts look a little too fatal for laughs. Dwight assures himself that the pumpkin will rot off his head in a month or two.
It's Halloween and the gang comes in costume, as usual. This year, Erin is a puppy (not a dog), while Pam comes dressed as Dr. Cinderella the Oncologist, putting a positive female role model spin on her daughter's current fascination with princesses. Jim claims to be one of the Men in Black guys, but in reality, he's just wearing his usual coat and tie; he's got an investor's lunch with his new sports marketing firm today and doesn't dare go in costume. Andy, in a leather jacket and a pair of aviators, struts in as George Michael and reminds everyone to finish their work (or throw it out) before lunch, since that's when the party will be starting. Moments later, he ushers in eight preppy college boys singing an a cappella version of "Karma Chameleon." Andy snaps his fingers along with them, overjoyed, while the rest of the staff looks confused. Dwight, donning a pig nose, looks particularly perplexed. The boys finish up, and the office awkwardly applauds them.
The boys are Here Comes Treble, an a cappella group from Cornell of which Andy is an alumnus. Andy's invited them to perform an entire set at the company Halloween party. To his uncontainable glee, Andy realizes they may even ask him to solo on what was his signature song, George Michael's "Faith." With one last go ahead from Pam, Jim heads off to the investment lunch. Meanwhile, Dwight is busying himself by eating a box of Nerds and making Erin snort with laughter when he tells her he's eating Jim. While cleaning up his mess, Dwight discovers a curious yellow pill beneath the couch. His thorough research uncovers that it's Dumatril, a pill prescribed to treat anxiety. Dwight immediately concludes that there's a madman in their midst, and he's determined to find out who it is.
Nellie assures Dwight that just because someone takes anti-anxiety meds doesn't mean the person's clinically insane. She adds that co-workers medical privacy should be respected. Off camera, we learn that the pill actually belongs to Nellie. She's not ashamed of her anxiety issues, but at the same time, she doesn't really care to share her condition with Dwight, who once yelled at Phyllis for sneezing incorrectly. In an attempt to get Dwight off her tail, Nellie agrees to help him find the office crazy. Meanwhile, Andy struts into the break room full of Cornell men, feeling like a king. He reminds us that he was a "freaking rock star" in college; when he got the nickname Boner Champ, he really grew into himself. Andy offers the college guys some intergenerational bro time, but no one really cares about the glory days. When Andy asks if they at least want to hear about how he got his nickname, one of the guys says he thought that Broccoli Rob was the Boner Champ. Andy can barely believe what he's hearing.
During the Halloween party, Pete admits he didn't know everyone at the office comes dressed up for the holiday. "Me neither" adds Creed, who's business casual attire is covered in suspicious blood spatter. In his office, Andy is video conferencing with Broccoli Rob, asking him why the Treble guys think that he's Boner Champ. Broccoli Rob admits that when he was talking with the gang about the old days, the wine coolers were flowing heavily, and the guys must have misunderstood him. Broccoli Rob promises to call the group and set the record straight.
Meanwhile, at Jim's business luncheon, Jim is a little out of place amongst the heavy hitters at the table. When he mentions he's interested in investing, the guys tell him it's already covered. But Jim, looking to appear successful and self-sufficient, offers up 10 grand; it's twice what he and Pam agreed upon.
At the office, Dwight is trying to sniff out just who might be crazy. He smears peanut butter across his face, trying to see if this plan to "keep his brain safe from the nanobots the governments puts in our air conditioning" seems crazy to Darryl, which of course, it doesn't. Andy returns to the break room, relieved that the guys now have confirmation that he is in fact Boner Champ. And how'd he get the nickname? By having sex with a snowman. The cold would have stopped most people, Andy explains, but he went right in. He couldn't be prouder of his story, but the Cornell guys shift in their seats uncomfortably. Angela, dressed as Nancy Reagan, ushers in Senator Robert Lipton, wearing a frighteningly realistic Ronald Reagan mask. Robert and Oscar exchange niceties, but when Robert starts saying how good it is to see him, Oscar quickly glances at the camera and hushes him.
Andy vents to Erin that Here Comes Treble didn't even know about the snowman story, and when they did hear, they didn't care. Out of love for Andy, Erin storms into the break room and demands that Here Comes Treble sing "Faith" later. It's not in their repertoire, they protest. "So learn it! You all go to Cornell," Erin yells at them.
In the kitchen, Dwight's placed the infamous pill on a plate and is sitting nearby, holding a huge net, hoping to trap the pill's true owner. Nellie's now in her costume: she's dressed as sexy Toby. She again tries to downplay the significance of the pill to Dwight. Toby strolls in the kitchen and is thrilled that Nellie is dressed up as him! He moves slowly towards her, first with confusion, then warm admiration, and finally... lust. It's an odd moment for all involved, and Toby rushes off. Nellie again tries to convince Dwight to call off the search. It's really not a big deal; everyone has anxiety
Meredith strolls into the kitchen and heads right for the pill, excited about finding a free upper. Dwight jumps up, quick as a cat, and captures her in the net. Nellie, unable to watch the shenanigans, frees Meredith from the net and admits to Dwight that the pill is hers, painlessly popping it into her mouth. Dwight's stunned.
In the conference room, as everyone waits for the concert, Pam is furious after finding out the huge sum that Jim ended up investing, when he didn't have to. Jim claims he had to look like a team player. Pam's yells are drowned out by the a cappella group pulling her chair forward and singing "I'll Be" to her. The concert continues, much to the disapproval of Dwight and Stanley, who look like they're in hell. Finally, the concert concludes with the boys singing "Faith" for Andy. As Andy gets up to wow the crowd with his signature song, he realizes Broccoli Rob is singing along with him, conferenced on the big screen! Here Comes Treble is under the mistaken impression that "Faith" is actually Broccoli Rob's signature song and that Andy just wanted to hear it. Andy's so shocked and hurt that he can barely speak.
Later, alone with Erin, Andy talks with Broccoli Rob via videoconference. He reminds Rob that a man's signature solo is his for life - that's group policy! Rob tells Andy it's not his fault that he lives close to campus and visits the group three times a week. The two former buddies get into a heated argument, complete with singing. Erin, horrified at their childish behavior, shuts off the monitor.
Outside, a still-angry Pam and Jim get into a heated conversation about the song "Monster Mash," using it as a metaphor for Jim's unnecessary spending. Kevin, not catching on, is in pure disbelief at how much Pam hates the Halloween tune, especially when Jim is making such great points for it!
Unable to let go of his past, Andy muses about moving to the Cornell area with Erin and setting up a happy new life there. Erin suggests that maybe he could just get more involved by being a mentor to some of the guys in the group. Instead, Andy decides to make a hefty donation to the group, via his mom.
Dwight, rethinking his stand on anxiety medication, now wants some of Nellie's pills. But he says it's not for him - it's for his poor, anxious cousin, Mose. Nellie understands his talking in code and tells Dwight she hopes "Mose" feels better. As Here Comes Treble sings off camera, we see the Office gang finishing up their Halloween day. Andy, dazed, wanders over to Erin's desk and tells her he just found out his parents are broke. Toby, looking head-over-heels, approaches Nellie with flowers, but turns the other way when she slips off her Toby wig and goes back to being regular Nellie. Outside, Oscar and Robert are caught in a passionate embrace by the cameras. It's been a wacky Halloween indeed.
Andy reunites with his a cappella group while Dwight deals with a drug scandal.