Dr. Brain

Composer

• 
  Mowg

Costume Designer

• 
  Cho Sang Kyung

Editor

• 
  Yang Jin Mo

Original Creator

• 
  Hongjacga

Screenwriter

• 
  Ko Yeong Jae
• 
  Kim Jin A

Screenwriter & Director

• 
  Kim Jee Woon

Main Role

• 
  Lee Sun Kyun

  Ko Se Won

  Main Role
• 
  Lee Yoo Young

  Jung Jae Yi

  Main Role
• 
  Park Hee Soon

  Lee Kang Moo

  Main Role
• 
  Seo Ji Hye

  Choi Soo Seok [Lieutenant]

  Main Role
• 
  Lee Jae Won

  Hong Nam Il

  Main Role

Support Role

• 
  Jo Bok Rae

  Sergeant Park [Lieutenant Cho's Partner]

  Support Role
• 
  Choi Hee Do

  Detective Choi

  Support Role
• 
  Moon Sung Keun

  Dr. Myung Tae Suk

  Support Role
• 
  Ahn Mi Na

  Yoo Jin

  Support Role
• 
  Cha Hee

  Dr. Hahn

  Support Role
• 
  Lee El

  Hyun Soo Jung

  Support Role
• 
  Yoo Teo

  Secretary Yoon

  Support Role
• 
  Lee Joo Won

  "The Fixer"

  Support Role
• 
  Kim Joo Heon

  Lim Jun Ki

  Support Role
• 
  Kim Min Seo

  Go Se Won [Teen]

  Support Role

Guest Role

• 
  Oh Yeon Ah

  [Se Won's Mom] (Ep. 1)

  Guest Role
• 
  Lee Ga Kyung

  [Principal] (Ep. 1)

  Guest Role
• 
  Jung Hyung Suk

  [Pediatrician] (Ep. 1)

  Guest Role
• 
  Choi Jae Young

  [Doctor] (Ep. 1)

  Guest Role
• 
  Joo Min Kyung

  [Doctor] (Ep. 1)

  Guest Role
• 
  Kim Jin Goo

  [Executive] (Ep. 1)

  Guest Role
• 
  Jeon So Nee

  [Reporter] (Ep. 1)

  Guest Role
• 
  Bae Jin Ah

  Dr. Han (Ep. 1)

  Guest Role
• 
  Kim Nam Woo

  Dr. Kim (Ep. 1)

  Guest Role
• 
  Kim Joong Hee

  [Japanese Restaurant Owner] (Ep. 1)

  Guest Role
• 
  Kwon Hyuk

  [ER doctor] (Ep. 1)

  Guest Role
• 
  Son Kyung Won

  [Morgue guard] (Ep. 1)

  Guest Role
• 
  Gong Sung Ha

  Mrs. Lim [Jun Ki's wife] (Ep. 1)

  Guest Role
• 
  Kim Geon U

  Se Won [Child] (Ep. 1, 5)

  Guest Role
• 
  Won Mi Won

  Jae Yi [from brain scan] (Ep. 2)

  Guest Role
• 
  Kim Min Ji

  [Jae Yi stand-in] (Ep. 2)

  Guest Role
• 
  Yoo Da Mi

  [Jae Yi stand-in] (Ep. 2)

  Guest Role
• 
  Jung Gi Sub

  [Coroner] (Ep. 2)

  Guest Role
• 
  Kim Jin Ok

  [Hee Jin's aunt] (Ep. 2)

  Guest Role
• 
  Lee Young Sook

  [Jae Yi's caregiver] (Ep. 2, 4)

  Guest Role
• 
  Um Tae Goo

  Tae Gu (Ep. 2-4)

  Guest Role
• 
  Lee Yoon Jae

  [Polygraph examiner] (Ep. 3)

  Guest Role
• 
  Lee Sol Gu

  Mr. Chang (Ep. 3)

  Guest Role
• 
  Park Ji Ye

  Mi Na (Ep. 3)

  Guest Role
• 
  Kim Kuk Hee

  [Madame] (Ep. 3)

  Guest Role
• 
  Heo Jin

  [Nam Il's mother] (Ep. 3-4)

  Guest Role
• 
  Cha Ji Won

  [Saera Children's Clinic manager] (Ep. 4, 6)

  Guest Role
• 
  Lee Sang Hee

  [Rest stop cashier] (Ep. 5)

  Guest Role
• 
  Kim Chul Yoon

  Sohn Il Ju (Ep. 5)

  Guest Role
• 
  Kim Woo Bin

  Jae Min (Ep. 5)

  Guest Role
• 
  Lee Seol Hee

  [ER nurse] (Ep. 1)

  Guest Role
• 
  Kim Eui Gun

  Detective Kim

  Guest Role
• 
  Kim Ji Won

  [Baseball girl]

  Guest Role

Unknown

• 
  Hwang Moo Young Unknown