The story begins with a 16 year old boy named Jack Johanson running away from home. After having wondered so far from his home, he happens upon a gem temple where he finds a gem artifact called "The Gem Of Size". Meanwhile, in Beach City, the Crystal Gems have returned from a mission. Later, they get word that Jack has broken into Fish Stew Pizza. The Gems head there, and Jack introduces himself and reveals that he has the gem of size. The Gems (minus Steven) are shocked at this revelation, with Steven wondering what it does. Pearl states that it can turn any living being colossal when embedded in it's chest. Jack applauds her for knowing, and reveals that he intends to do just that, then take his revenge on all who have wronged him. Just then, he drives the gem into his chest, and turns 50 feet tall, dubbing himself "Gemzilla" before going on a rampage through Beach City. Even the combined efforts of the Gems aren't enough to stop him, and he lays waste to much of the city. When Jack sees Connie, he realizes that Steven has a fondness for her, and kidnaps her, then climbs to the top of the tallest building in Beach City. Jack tells the Gems that if they surrender, he will give him a place in his new empire, but if they don't, he'll drop Connie. When the Gems refuse, Jack states that they have no choice, and that he won. Garnet, Amethyst, and Pearl fuse into Alexandrite and climb up after Jack. Jack then drops Connie before grabbing Alexandrite, picking her up, and throwing her off the building. Alexandrite clings back on, grabs Jack by the ankle, and pulls him down, with him grabbing on. Alexandrite states that Jack is a worthy adversary, but the fight is hers, and tells him to surrender. Jack states that he'll never surrender. In a last ditch effort to destroy the Gems, Jack knocks down the top half of the building, which falls on top of Jack, Alexandrite, and Steven. Steven is protected by his bubble, but Alexandrite is defused into Garnet, Amethyst, and Pearl again. Connie then comes out, revealing she landed on a pile of oranges. Jack then comes up out of the pile of rubble, then leaves, stating the gems haven't heard the last of him. Amethyst then states that Jack "has some MAJOR issues".
