Finn practices his sword fighting skills at the candy junkyard, where he meets an old gumball robot named Rattleballs. To Finn's shock, he finds out he's NOT the master swordsman he thinks he is. What the what?! Finn begs Rattleballs to train him, but he soon discovers his mentor's deep, dark secret... a secret that will ultimately test Finn's loyalty to Princess Bubblegum.

In Wizard City, a magic spell backfires and turns Ice King back into Simon. Now with Finn, Jake and Marceline's help, Simon finds a way to bring his beloved Betty back. Finally reunited with the love of his life, everything is great! There's just one catch...without his magic crown, Simon will die.