Season 1

The mysterious Baek family moves to Kumsu city and opens the "Pawfect Haven Animal Hospital." The same day a young woman, Lee Yu-jin, is reported missing in Kumsu mountains. Worries of a serial killer called "Doom-veloper" surface. The Baek family son, Ji-hoon, and daughter, Ji-woo, are threatened by local bully Jo Kyu-tae. They decide to take their problem home to Mother, Han Young-su, to remedy.

Mother gives Kyu-tae a "treatment" and he reveils that Park Jae-gon, the student president, is actually the school's Sex Crime Ring Lord. Jung Ho-chul, the murderer, escapes from the Baek's. The Baek family turns over Lee Yu-jin's body to the police.

Detective Kang Jeong-hwan and Officer Oh Man-joong of the Homicide Squad question the Baeks. Ji-hoon's investigates the sex crimes and uncovers Jang No-won, Director of Urban Development, is the lead instigator. Jo Hae-pal, the National Gang Boss and restrauant owner, kidnaps Ji-hoon and Kwon Min-jung in retaliation for Young-su's treatment of his son.

Young-su exacts justice for Shin Ju-kyung and her father while Baek Cheol-hee, Father, goes to rescue Ji-hoon and Kwon Min-jeong. Young-su confronts Yoon Myung-hwan, Pastor of Aspirations Church about No-wan's sexual crimes. Detective Kang goes to the animal hospital to confront Cheol-hee only to have Jung Ho-chul arrive to kill Cheol-hee.

The reason for the Baek family move to Kamsu is revealed. Detective Kang finds out who the Baeks are. Chief Oh and Ryu Mi-ok, Number 12, capture Young-su and Ji-won to harvest their organs. New facets concerning Pastor Yoon are revealed.

Doom-veloper comes out of hiding. Young-su strives to save Cheol-hee but the family falls into disarray and is confronted on three fronts.