Sisterly sparks fly when Jennifer decides to date the younger brother of Mallory's former high school heartthrob.

As the Keatons try to persuade Steven that he needs a relaxing hobby, Jennifer nervously awaits the arrival of her new friend, Josh Wakefield, who has agreed to work with her on a project for the French Club. When Mallory realizes that Josh is the younger brother of Jeff Wakefield, her former high school boyfriend, she becomes overprotective and reminds Jennifer how Jeff jilted her when he went to college. Mallory just assumes that Josh will do the same to Jennifer.

Mallory's distrust of Josh increases when she learns that he intends to attend Jeff's alma mater, Princeton. After sharing her misgivings with Elyse and learning that Josh has asked Jennifer to the prom, Mallory decides she must confront her sister. Jennifer, who is very excited about her new relationship, resents Mallory's assumptions about Josh and the sisters begin to argue. Finally, Nick suggests to Mallory