K-dramas are known for their romantic, historical, and revenge-based storylines, but hidden in between the most popular genres are detective stories. The best detective K-dramas contain a well-written mystery that even its most attentive viewers won't be able to solve right away. Many detective series follow a similar formula in which its protagonists are compelled to return to crime-solving after leaving their jobs due to traumatic events. Such is the case in K-dramas like Hello Monster and Tell Me What You Saw.

Others in the genre, including He Is Psychometric and Inspector Koo, shake things up and include greater hints of comedy and romance than what is typically expected of a detective series. Regardless of how firmly a series adheres to the expectations of the genre, one thing is for sure: the best detective K-dramas keep audiences second-guessing their instincts until the last episode.

10 Mouse (2021)

A detective attempts to catch a dangerous serial killer

Just like quite a few other crime thriller K-dramas, Mouse is inspired by real-life events. Screenwriter Choi Ran found inspiration in a 2017 South Korean murder case in which the killer showed zero signs of remorse while appearing in court. Ran was fascinated by the killer's response and decided to create a show in which the murderers reflect on their actions, as such a realization would be a form of punishment in and of itself.

Mouse is centered around killers with psychopathic tendencies that are investigated by Detective Ko Moo-chi (Lee Hee-joon) and his partner Jeong Ba-reum (Lee Seung-gi). Mouse provides K-drama fans with an absorbing mystery, but some complex themes are explored as well. As they're hunting down the killer, Ko Moo-chi and Jeong Ba-reum dive deep into psychopathic behaviors and how those traits come to be.

9 He Is Psychometric (2019)

A man uses his ability to access the past to solve a criminal case

He Is Psychometric is a procedural series that fuses a few different genres, including romance, comedy, and fantasy. The K-drama revolves around Lee Ahn, played by Got7 member Park Jin-young in his first leading role. Lee has the ability to read a person or object through the use of physical — known as psychometry — and uses his gift to solve a case that's weighed heavy on him and his friends.

The budding romantic connection between some of He Is Psychometric's characters doesn't take away from the series' central mystery.

Differing from other detective K-dramas mentioned, He Is Psychometric has a side romance. One of Lee's friends, Yoon Jae-in (Shin Ye-eun), is a bit closed off, but Lee uses his ability to help her heal from her hidden past. However, the budding romantic connection between some of He Is Psychometric's characters doesn't take away from the series' central mystery.

8 Tell Me What You Saw (2020)

A profiler works with a team of detectives to catch his fiancée's killer

Jang Hyuk leads Tell Me What You Saw as Oh Hyun-jae, an esteemed profiler who secludes himself from others after his fiancée tragically dies. However, Hyun-jae is back on the job a few years later after a crime similar to the one that killed his fiancée is committed. Hyuk is ed by a handful of actors like Choi Soo-young, Jang Hyun-sung, and Jin Seo-yeon, who play an assortment of detectives that help Hyun-jae catch the serial killer.

Tell Me What You Saw does have a few narrative missteps and certain episodes make it apparent that the series was beginning to lose steam. Still, Tell Me What You Saw presents a strong mystery where every person involved in solving the case has their own motives. For Hyun-jae, his motives are personal and Hyuk does a great job capturing the toll such an investigation has on his character.

7 Hello Monster (2015)

Two detectives are caught in a cat-and-mouse game

Despite earning less than impressive ratings, Hello Monster still managed to earn praise from critics and audiences as the thrilling police procedural has an enticing narrative and stellar performances. Hello Monster begins with profiler Lee Hyun (Seo In-guk) who returns home to investigate his father's death. Meanwhile, his colleague, Detective Cha Ji-an (Jang Na-ra), has begun her own investigation into Lee Hyun.

The two eventually cross paths and uncover a truth that's more twisted than either of them could have anticipated. Due to the writing and structure of the series, audiences are guaranteed to be completely enthralled by Hello Monster's mystery and just as shocked as its characters are by the series' reveals. Seo and Jang are strong leads in the series, each earning a handful of award nominations for their performances, but it's Park Bo-gum's performance that captivated audiences and earned Hello Monster its two wins during award season.

6 Class Of Lies (2019)

A former lawyer goes undercover in a high school

Rather than take place in the streets of a populated South Korean city, Class of Lies is predominately set in a private high school. Class of Lies follows Gi Moo-hyeok (Yoon Kyun-sang), a respected lawyer who gets his license to practice suspended after he's surrounded by allegations of bribery. Gi then adopts a fake name, Gi Kang-jae, and takes a teaching job at a high school plagued by the mystery of a student's murder.

During his undercover work, Gi Kang-jae discovers a secret about the school's privileged students. Despite their wealthy upbringing, the high school students in Class of Lies are never presented as shallow stereotypes of rich kids. Instead, Class of Lies is sure to include commentary on the outcomes that stem from an unchecked, highly connected environment. Still, audiences root for Gi Kang-jae to break through the connections of the high school and find the real murderer.

5 Inspector Koo (2021)

An insurance investigator uses her prior detective knowledge to solve a case

Once an accomplished police officer, Inspector Koo's titular character turns to alcohol and gaming after the death of her husband. However, Koo Kyung-yi (Lee Young-ae), now an insurance investigator, makes a return to her crime-solving days after she suspects a serial killer is orchestrating murders to appear as accidents. Lee Young-ae, known best for her role in the historical K-drama Jewel in the Palace, completely transforms for her portrayal of Koo Kyung-yi.

Though there is an intriguing mystery at the center of the series, Inspector Koo is not as intense as other detective series. There are plenty of suspenseful moments throughout, but Inspector Koo acts more as a blend between thriller and slice-of-life K-dramas. The latter genre is made clear by the assortment of eccentric characters surrounding Kyung-yi, such as the titular character's friend Han Kwang-wook.

4 Partners For Justice (2018-2019)

A forensic doctor and a prosecutor team up to solve cases

In Partners for Justice, Baek Beom (Jung Jae-young) is a forensic doctor who teams up with prosecutor Eun Sol (Jeong Yu-mi). Together, the two solve a series of cases. The two have mismatched personalities at the start, which makes for some entertaining interactions between them. However, they end up being a strong team, as seen throughout Partners for Justice's two seasons.

Each case holds a varying level of stakes, with some cases being wrapped up sooner than others, which ensures audiences are rarely ever able to predict how and when Baek Beom and Eun Sol will solve a case.

What makes Partners for Justice a solid detective series is its sharp writing and well-crafted plot twists. These factors not only draw audiences in and keep them invested, but they also allow for more varied cases as the series progresses. Each case holds a varying level of stakes, with some cases being wrapped up sooner than others, which ensures audiences are rarely ever able to predict how and when Baek Beom and Eun Sol will solve a case.

3 Vagabond (2019)

Two people team up to uncover a government conspiracy

It appears a government conspiracy is tied to a mysterious plane crash and Vagabond sees an ordinary stuntman stepping up to uncover the truth. Cha Dal-gun (Lee Seung-gi) is a stuntman whose nephew was killed in a plane crash he's not sure was an accident. Therefore, Dal-gun teams up with covert operative Go Hae-ri (Bae Suzy) to find out what really happened.

Vagabond does end on a cliffhanger that has yet to be resolved, as no news about season 2 has been announced. Still, Vagabond season 1 is full of exceptional action sequences and a series of unexpected plot twists that keep audiences engaged until the very end. Dal-gun and Hae-ri are each compelling characters in their own right, but the latter has a determined attitude that makes her a likable character and one of the toughest female K-drama leads.

2 Flower Of Evil (2020)

A wife becomes suspicious of her secretive husband

At the center of Flower of Evil is a seemingly perfect married couple, Baek Hee-sung (Lee Joon-gi) and Cha Ji-won (Moon Chae-won). From the start, neither party is fully trusting of the other, but Ji-won becomes increasingly suspicious of her secretive husband after her detective job sends her down a rabbit hole of unexplained murders. As exciting as a shocking ending in a detective series can be, there's always a risk of losing audiences' attention before the big reveal is made.

However, Flower of Evil ensures this never happens. With each episode, subtle clues are dispersed throughout that hint towards the series' biggest reveal. Aside from the mystery, Flower of Evil's leads do a brilliant job of pulling audiences in. Joon-gi effectively portrays the enigmatic Hee-sung and Chae-won strikes the ideal balance as a wife playing it cool to not interfere with her outside investigation.

1 Signal (2016-Present)

Two detectives from different decades solve cold cases

Signal is recognized as one of the highest-rated K-dramas in cable television history, and it's easy to see why. The gripping series has elements of time travel K-dramas as its narrative interweaves two timelines, one taking place in 2015 and the other in 1989. This is explained by a mysterious walkie-talkie discovered by criminal profiler Park Hae-young (Lee Je-hoon). The discarded device allows him to communicate with Detective Jae-han (Cho Jin-woong) who's living in the past.

Together, the two effectively work to solve a series of cold cases. Signal gets its inspiration from the 2000 film Frequency, as well as a series of murders in South Korea that took place between 1986 and 1994. However, Signal doesn't aim to replicate the events of its inspirations piece-by-piece, leaving plenty of room for unpredictable plot twists that keep audiences guessing.