It's Halloween time at Greendale Community College, and the gang is all dressed up and ready to go to Vicki's party. Abed and Troy are going as Calvin and Hobbes, respectively, and Jeff is in the costume of an old time boxer. His date for the night, Annie, comes in dressed as the creepy girl from the Ring, misunderstanding Jeff's text message asking her to come as his "ring girl." Abed hopes there is a TV at the party, as Cougar Town is having their Hallo-wine episode and watching Annie watch that show... is his third favorite show on television. Before they take off, however, Pierce texts Troy to let him know he's been locked in his panic room. The gang sets off to bail him out.
At Pierce's mansion, Troy leads the group to the panic room, one of the 27 stops he had to memorize in the house before moving in. Inside, Pierce is embarrassed to admit that he may have accidentally bumped a switch when he was dusting inside earlier. He apologizes for being a burden... and wallows in his own misery by wondering if that's all he is anymore. After Pierce explains that the code to open the door is in a red notebook somewhere around the house, the group is determined to help him escape his locked confines. But Jeff isn't fooled - he knows Pierce is hiding something. Pierce admits the dusting story was a lie, but he says he made it up only because the real story - the one in which he locked himself in after seeing something that scared him to death - was too embarrassing. As the group sets out to investigate the house, a shadowy figure lurks in the foreground.
As Jeff and Britt search Pierce's bedroom, they realize the mansion is spookier than they originally thought. Britta decides to capitalize on the opportunity by using it to practice her therapy training on Pierce. When Jeff shows irreverence towards an old photo of Cornelius - Pierce's father - Britta freaks out and ponders the idea of the old man's ghost haunting the mansion. In an attempt to belittle her naive anxieties, Jeff goes off on a tangent that accidentally dips into the emotionally personal... catching himself, he scoffs at Britta's attempt to delve into his psyche.
In the study, Annie searches through a desk for the notebook, while Abed unlocks a secret passage to Pierce's surveillance room by messing with a bookshelf. It is undeniably the greatest moment of his life to date. When Annie turns around, her companion is gone, and she is thoroughly spooked. Walking through abandoned halls, Annie laments on the horror movie cliches that are causing her to worry. Elsewhere, Shirley tries to preserve Troy's innocence by shepherding him away from a bizarre S&M room in the mansion, which he - in his childish ways - confuses for an indoor swing set. Annie runs into the two in the hall and explains how she lost Abed. While the group panics, Abed enjoys Cougar Town in the surveillance room.
Back in the bedroom, Britta and Jeff are arguing about her forced therapy. She feels he has daddy issues and could be turning into Pierce. He vehemently disagrees with this notion. Jeff pulls out his father's number on a notecard - which he's had for weeks - to help illustrate how few daddy issues he has. After all, if he really were emotionally disrupted, wouldn't he have called by now? Realizing Jeff found his father, Britta's guard momentarily comes down as she leaps unsuccessfully for the notecard. Watching from the surveillance room, Abed ponders back to the times when this show was about a community college. As he rewinds some footage, Abed finds a clip of a shadowy figure standing over Pierce's bed as he sleeps. The plot thickens.
Jeff hides inside of Pierce's library after escaping from Britta, who's dead set on possessing the number of Jeff's father. Inside, Jeff finds a red notebook with the panic room code inside. Meanwhile, Annie, Troy and Shirley are convinced that Jeff was right and that Pierce was stringing them along the entire time. Nevertheless, Troy insists they venture onward, as he's eager to find his friend Abed. At the same time, eerie things begin to happen all around the mansion. The library, where Jeff is, begins to shake violently and the portrait of Cornelius begins to warp. As Annie, Troy and Shirley travel down the hall, one of the walls takes the form of a human and reaches out to grab Troy. Both groups bump into each other as they run screaming down the hall.
Back at the panic room, the gang finds out that Pierce is now dead inside, which makes everything a hundred times worse. After keying in, they find the room empty, only to be pranked by Pierce, who enters gleefully. He faked the haunted house as a means of getting back at them for planning to attend Vicki's party without him. Abed enters the room and reveals Pierce's plan... a minute too late. As he plays back the montage of Pierce's tricks, even the perpetrator himself is surprised at the footage of the shadowy figure over his bed. He didn't take part in that stunt.
Now that everyone in the mansion is convinced of paranormal activity, Pierce shuts the panic room in a... panic. Just after the door shuts, someone punches the code in from the outside and enters the room. It's Gilbert. It's revealed he was the shadowy figure standing over Pierce's bed. It appears that, after a lifetime of assistance, Gilbert has had trouble dealing with Cornelius' passing. Pierce offers to bring Gilbert in as his roommate. The two embrace, and Jeff is moved by the moment. As the gang sets off for the party, Jeff departs, as he has business of his own to attend to; back at his place, Jeff pulls out his father's phone number and gives him a call.