Lee Seung-noh

An inspector from the Educational Rights Protection Bureau (ERPB) who is authorized by the government to use physical intervention and unconventional methods to discipline delinquent students and reform the educational system.

While hiding a kidnapped target, a contract killer’s cover unravels when he falls for the detective hunting the truth.

Humming centers around the relationship between a sound engineer and a supporting actor working on the post-production of an unfinished film, along with the anecdote of a deceased actor.