Epidemiology

The study group eats taco meat from army surplus while discussing costumes.

Pierce becomes ill and Annie gets help from Rich.

Troy and Abed's costume antics fail to impress two female students.

Dean Pelton sends more sick students to Rich for treatment.

Pierce suddenly bites Star-Burns' arm during diagnosis.

Annie theorizes Pierce transferred sickness to Star-Burns through a bite.

Dean Pelton calls the food supplier and mentions a key phrase.

Rich warns Jeff about the infection and a zombie panic breaks out.

The study group barricades themselves in a room to escape the zombies.

Rich explains the infection leads to brain damage in three hours and death in six.

The group argues about whether to stay or go to the thermostat.

Rich reveals he was bitten and starts showing symptoms.

The group splits up as zombies attack, with some escaping.

Troy and Abed hide in a basement and argue about costumes.

Troy and Abed are distracted by a cat in the basement.

Troy escapes through a window while Abed is left behind.

Troy decides to put on his costume and go to the thermostat.

Troy fights zombies but is bitten by Abed.

The army arrives and knocks everyone out with gas.

Police and EMTs arrive; Dean claims everyone was roofied.

Troy and Abed decide to watch a light movie, avoiding zombies.

Chang leaves a voicemail claiming he and Shirley did it.