After a particularly hard history test, which even Jimmy found challenging, Sheen claims to have found it easy. Suddenly Ms Fowl calls him back, which Sheen thinks is to compliment his test. However, it turns out that Sheen has failed, and needs to ace the maths test to avoid being kept back.
Sheen begs Jimmy to help him, saying that he cannot be held back AGAIN. Jimmy agrees, and him and Carl set to work. They try to get him to pay attention through negative-reinforcement, giving him a zap every time he is distracted. Despite this, he still cannot concentrate, and soon he seems doomed. Jimmy finally decides to turn his 'brain-drain' helmet into a 'brain-gain' one.
It works well, and Sheen becomes a genius. He easily aces the maths test, getting all the answer correct. But his brain keeps growing, and when Jimmy asks him to get his intelligence sucked away, he uses some acquired telepathic powers to throw Jimmy off. Then he declares himself the supreme ruler, and takes Libby as his queen.
Jimmy tries to convince Sheen to put the helmet on by disguising it, knowing that otherwise, Sheen's head will explode. But Sheen is stubborn and gets Carl to put on the helmet for him. Whilst Carl holds the helmet, he thinks about what he is concealing, and Sheen reads his mind.
Jimmy is ready to give up, but Carl convinces him to keep trying because Sheen is still their friend on the inside. And so Jimmy gets an idea. He and Carl get into an Ultralord suit and try to convince Sheen to put on the helmet. But Sheen still resists and throws back Ultralord, causing Jimmy and Carl to be thrown out, wounded. Sheen sees them and suddenly feels sad. Finally, he puts on the helmet and everything goes back to normal.