Amy experiences strange symptoms, which she believes are signs of a flu. They include an elevated heart rate, sweaty palms, dry mouth, and localized vascular throbbing. As Penny and Bernadette were present when the symptoms began, they know that Amy doesn't have the flu: she is in lust with Penny's ex-boyfriend, Zack Johnson. As Amy and Sheldon finally come to the conclusion that Amy is feeling womanly urges for the first time in her life, Sheldon has to come to terms with what his feelings for Amy are. They also have to decide how best to satisfy Amy's new biological urges. Meanwhile, Howard and Raj get into an argument: if they were to acquire super powers, who would be the superhero and who would be the sidekick. They have to come up with a way to settle the argument.