When Britta's old flame "Blade" returns to town with the traveling carnival, she confesses to the group that she needs their help to stay away from him. While Annie, Troy and Abed scheme to keep her occupied and away from Blade, Jeff and Shirley head to the carnival to get a look at the mystery man. Meanwhile, Dean Laybourne enlists the help of Dean Pelton to convince Troy to join the Air Conditioning Repair Annex.

When Annie discovers the study group's yam experiment smashed to smithereens on the science lab floor, the group mobilizes to expose the criminal and save their grade. Once Abed and Troy think they have located the perpetrator, the group conducts a "trial," with a reluctant Professor Kane serving as judge. Jeff soon realizes, however, that the plot is thicker than anyone suspects.