The first day of school is upon the Heck family, and Sue finds herself feeling a sense of freedom she's never felt before with Axl not around to make her campus life miserable. But Brick, who is beginning middle school and afraid of getting a swirlie, avoids the bathroom at all costs. Meanwhile, Frankie becomes jealous of Mike when she discovers that Axl calls and returns his texts but won't do the same for her; and Sue's feelings for Darrin surface once again when Mike calls him over to help fix the air conditioner.

Marking the 100th episode milestone of "The Middle," the citizens of Orson, Indiana celebrate the Orsontennial - the town's 100th anniversary. During this momentous event, Frankie and Mike find themselves begrudgingly trying to drive a giant cow float in the parade; Axl, Sean and Darrin resurrect Boss Co. and attempt to make some big bucks by setting up a VIP area to view the festivities; Sue, still crushing on Darrin, tries to make him jealous by pretending to be dating Brad again; and Brick tries to earn himself a place in Orson history by entering a contest to come up with the town's new motto, which will be used for the next 100 years.