Sheen is one math test away from being left back, so Jimmy turns his Brain Drain helmet into a Brain Gain helmet and uses it on his buddy, instantly quadrupling Sheen's IQ. With his new and improved brain, Sheen aces the math test in record time and passes the class. But his brain is still gaining, and soon Sheen develops the power to read thoughts and move objects with his mind. If Jimmy doesn't reverse the effects of the Brain Gain helmet, not only will Sheen's power continue to increase, his brain could grow until it explodes.