Sky Wongravee, a brilliant and rebellious senior, finds himself constantly at odds with Professor Nani Hirunkit, the cold mathematics professor known for being strict. When Sky's close friend is suddenly expelled, he suspects professor Hirunkit to be a part of it. Determined to expose the truth, Sky blackmails Nani into tutoring him privately. But as equations give way to tension and resentment turns into obsession , Sky discovers that the professor he hates may be hiding wounds deeper than the ones he's caused.