An affair is a forbidden act in which a man falls in love with another woman despite having a wife - and it's between a teacher and a student. He knows it's wrong. The more he thinks it's wrong, the more excited he gets! The other person is Mao, the most serious and top student in the class. The student and teacher are attracted to each other and have a secret rendezvous at a hotel. They get so close that their reason breaks down. They passionately kiss as they desire each other. Sex is so thrilling it makes their brains melt. They continue to desire each other all night, staying together until the morning. The events of one night drive this dull middle-aged teacher crazy.