In 2039, a plague called "mute disease" broke out. It spreads through language - people who speak certain words will be infected, gradually lose their language ability, and eventually become "mute" who can only pronounce meaningless syllables. The infection rate is positively related to the "emotional concentration" of the vocabulary: Saying "I love you" is 10,000 times more likely to be infected than saying "The weather is nice today." Human society has fallen into silence, daring not to speak, not to write, not even to think about emotional words. The only one immune is an undeciphered dialect of Sumerian, an ancient language that has been "dead" for three thousand years.
