Frank swaps an evil crystal with the magic crystal, to turn Princess Butterfly evil.

After her transformation, King Boogieman goes to Rose and Petunia's school (frightening many children in the process) to get their help.

They get back to find Evil Butterfly (as nicknamed by fans) has destroyed half of Butterfly Valley.

All of the trolls help the fairies put out the fire.

The rest of the episode details Franks evil plan to take over the world, and Evil Butterfly becomes attracted to Frank.