After. A delivery error causes a coffee called "Lotta Latte" to turn its drinkers into zombies. The principal of White Chapel High has a whole case delivered for the teachers to celebrate "100 Days Until Summer Vacation" and all the teachers turn into zombies. They decide to blast the air conditioning to subdue the zombies. Sarah hurries to the room where the heating/AC controls are but while she tries to find the right switch for the A/C, she is attacked by the zombified Rory, who had been in the teachers' lounge. Meanwhile Ethan is trapped in the chemistry lab with the zombified adults and zombified Benny and tries to avoid getting bitten. Sarah fights off Rory, slamming him against the A/C switch. The A/C turns on and the zombies turn back to normal.
After. A delivery error causes a chicken restaurant's Liquid Chicken Debrainer to be sent to a coffee shop, which causes the coffee to turn drinkers into flesh-eating zombies since they mixed the coffee mix with live chicken parts. The principal of Whitechapel High Mr. Hicks has a case of the contaminated coffee delivered for the teachers to celebrate "100 days until summer vacation", turning the entire staff into zombies. Ethan and Benny warn the school over the PA system, but are trapped in a classroom. Ethan discovers that the zombies are repelled by the fire extinguisher and attempts to hold them off until Sarah returns from a field trip to an art gallery. Upon her return, they split up to find a cure: Sarah races to Ethan's house for a microscope part, discovering in the process that Ethan's mom has been turned into a zombie also. Ethan and Benny sneak into the teacher's lounge to get a sample of the coffee and return to the chemistry lab to continue their investigation. Inspecting the molecules, Ethan determines that the zombies are averse to cold temperatures, explaining their reaction to the fire extinguisher's foam substance. Sarah hurries to the heating/air conditioning control room, but is attacked by a zombified Rory in the process. Meanwhile, Ethan discovers that Benny was bitten by a zombie but was reluctant to inform him, and becomes surrounded by zombies, including Benny. Sarah is able to turn the air conditioning on in a scuffle with Rory, stopping the zombies cold and returning them to their original human forms.