Spike sneaks into Zecorah's place and 'borrows' a special flower. Smelling it will make toi fall in l’amour with the first person toi see. Obviously he tries to get Rarity to smell it, accidentally infecting everyone in ponyville in the process. Eventually everypony's chasing Spike in a lovestruck stampede, causing Celestia to come down from her château to see what the ruckus is about. When she too smells the fleur and falls in l’amour with Spike all hell breaks lose.
Spike is forced to ask Zecorah for help. She creates a rose nuage of fog, that cures everypony. Luckily for Spike nopony remembers a thing. In the end he writes a letter to Celestia, about how l’amour is something that cannot be forced.