- Seo In-guk (Lee Hyun)
- Jang Na-ra (Cha Ji-an)
- Park Bo-gum (Jung Sun-ho/Lee Min)
- Lee Chun-hee (Kang Eun-hyuk)
- Choi Won-young (Lee Joon-ho/Lee Joon-yeong)
- Im Ji-eun (Hyun Ji-soo)
- Min Sung-wook (Son Myung-woo)
- Kim Jae-young (Min Seung-Joo)
- Jun Kwang-ryul (Lee Joong-Min)
- Son Seung-won (Choi Eun-Bok)
Hello Monster — S1E2
Episode: Hello, Monster
Air Date: 2015-06-23
Runtime: 59 min
Overview
Plagued by insidious thoughts planted by serial killer Lee Joon-Yeong and recent events; Lee Hyun's father believes that he is becoming a monster. He isolates him in the basement to protect both him and the world. Joon-Yeong escapes from prison, murders his father and absconds with his brother. Lee Hyun discovers a painting at a murder scene that he believes may be his brother Lee Min’s.