Spike sneaks into Zecorah's place and 'borrows' a special flower. Smelling it will make te fall in Amore with the first person te 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 castello to see what the ruckus is about. When she too smells the fiore and falls in Amore with Spike all hell breaks lose.
Spike is forced to ask Zecorah for help. She creates a rosa nube, nuvola of fog, that cures everypony. Luckily for Spike nopony remembers a thing. In the end he writes a letter to Celestia, about how Amore is something that cannot be forced.