Beneath the human community, lies centuries secret of the complex wolf/werewolf community. When Kai, a teenage wolf failed his crucial third trail and was condemned for execution, he fled into human society to seek refuge. By twist of fate he encountered D.O, a werewolf hunter with a problem of his own. Together they formed an unlikely bond and teamed up to investigate the recent grisly murders in the city as well as to solve the mystery behind Kai's failure in his third trail.  

Aspiring singers, bandmates from a school in Seoul; Suho, Baekhyun, Sehun and their Chinese tranfered friend Tao went to Busan to try to expand their music career. While Suho went away from the group to try to strike deal with an accomplished recording company, the rest of the members enjoyed their once in the lifetime holiday in Busan, courtesy of Tao's wealthy family to provide the friends 5-stars hotel to stay.