As the head of the 112 emergency call center, Kang Kwon Joo (Lee Ha Na) carries a lot of weight on her shoulders. Using her incredibly enhanced hearing ability to better understand the calls coming into the center, Kwon Joo has helped save countless lives. But when a new serial killer begins to wreak havoc, Kwon Joo’s skills are put to the ultimate test. Using enhanced hearing abilities of their own, to hunt down their next victim, this new serial killer always seems to be one step ahead of those who seek to bring them to justice. Driven into a corner, Kwon Joo has no choice but to team up with Detective Derek Jo (Song Seung Heon), a team leader from the Los Angeles Police Department, temporarily assigned to the case. A man of principle, Derek has dedicated his life to taking down criminals and his impressive record shows he has zero tolerance for mistakes. Combining their knowledge and their skill, Kwong Joo and Derek make a formidable force. But will their combined skill be enough to catch the killer before they strike again? The fourth season of the wildly popular series, “Voice 4” is a 2021 action crime thriller drama directed by Shin Yong Hwi.