The story follows the legend of the three wise monkeys—Mizaru (see no evil), Kikazaru (hear no evil), and Iwazaru (speak no evil). J.D. Barker introduces a terrifying , Shizaru, representing "do no evil".

: Detective Sam Porter finds a personal diary on the body, which reveals the killer’s chilling childhood and suggests one last victim is still alive and hidden. The "El Cuarto Mono" Trilogy

: Known as the 4MK Killer , the antagonist kidnaps victims and sends three white boxes to their families: the first containing an ear, the second containing eyes, and the third containing a tongue.

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