Journalist Shuichi Fujii receives a letter from convicted killer Junji Sudo. Writing from death row, Sudo wants to confess to crimes unknown to the police. On visiting Sudo in prison, Fujii learns about a real estate broker called 'Doc' who masterminded a string of murders that Sudo worked muscle for. Set up by Doc, Sudo seeks revenge and implores Fujii to find the evidence needed to bring in his former boss. Working off Sudo's sketchy memories, Fujii begins to piece together a grizzly tale of extortion, torture, rape, and arson. But as his desire to see Doc brought to justice nears the boiling point, he runs into resistance from his editor, who views the story as tripe, the police, who seem indifferent to the case, and his wife, who is at her wits' end dealing with his mother's increasing dementia. Based on true crime cases, 'The Devil's Path' exposes the secret underbelly of crime in modern Japan.
