It's frowned upon to go back on your word.
Charles, a journalist, invites Martin, a criminal with a record, to an interview and promises him safety from prosecution.
Charles wants to keep Martin from committing more crimes.
Charles has the interview and tries to convince Martin to leave a life of crime.
Charles contacts the police and has them show up at the meeting and arrest Martin.
Martin sees the need for change and promises to leave crime.
Martin is very angry and spends his entire prison term plotting revenge against Charles.