Understand (Chiang)
A man named Leon had a near-death experience falling into icy water, causing him to fall into a coma due to extensive brain damage. When he awakened from the coma, he discovered that he had been treated with a new experimental drug called hormone K, a therapy aimed at regenerating damaged neurons.
Over time, he realized that his brain functionalities, intelligence, and comprehending capabilities have significantly improved beyond normal human capacity. As he progressed, he was able to multitask, reading and editing holographs while simultaneously having a telephonic conversation.
He's surprised. Most people can't retain so many digits if they've only heard them once. Do you use mnemonic tricks?
He even developed the ability to absorb and manipulate an enormous amount of knowledge, revealing the universe's intricate patterns and gestalts.
With my mind's language, the distance between myself and enlightenment is precisely calculable. I've sighted my final destination.
He then requested another injection of hormone K to further enhance his cognitive abilities, leading to him gaining the ability to control his body to an unnaturally advanced degree. However, his newfound intelligence and abilities garnered the attention of the CIA, who wanted to contain him for study and potential use as a strategic tool. In order to evade the agency's control, he fled, carrying with him an ampule of the experimental hormone K. He eventually injected himself again, taking his cognitive abilities to yet another unprecedented level. He was eventually discovered by another individual who had also received a high dose of hormone K, leading to a battle of these extraordinary minds, culminating in his adversary using a memory-trigger invoking a lethal realisation, causing Leon's mind to effectively dissolve.